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How To Upgrade a 2008 Ford Mustang Shelby GT Convertible
Updated and Upgraded - Tweaking a special S197 Mustang to make it the perfect road car
Let’s begin with the confession; the Vista Blue ’08 Shelby GT ragtop you see in these photos is my own personal car. I’m not, for a second, going to say it’s perfect; I can only tell you what it is, what it is not, and what I’ve done to make it my own and I believe, a nicer car.
When the S197 Mustang came out for the 2005 model year I immediately decided I had to have one. Ah, but which? I didn’t know, but decided to wait past the intro model year, thinking that the convertible body style would soon be on its way, along with a multi-year rollout of special and high-performance models. When Shelby got back into the Mustang business with the GT-H in 2006, I felt that just might be my ticket in; who doesn’t love that black and gold Hertz-Shelby livery, and I’ve always wanted a Shelby Mustang. But that car was automatic trans only, and I’m a stick and clutch kind of guy. Then along came the G.T. 500 a year later, and I thought that might be the thing for me. Yet my dithering continued.
Shelby launched the GT model for 2007, and I immediately liked the mix; a Shelby-built Mustang, naturally aspirated with enough content to be worthwhile, and it was actually affordable. Initially, that car was offered in coupe form only (painted black or white, with silver stripes), but it wasn’t long before I’d heard that a convertible version was on its way for 2008. Along with a new color offering: Vista Blue Clearcoat metallic. The package was just what I wanted; and with the black vinyl–covered sport bar in back, it reminded me of the ’68 G.T. 500KR I’d long lusted over, but could no longer afford.
I was Executive Editor of Motor Trend magazine at the time, and my responsibilities included the selection and ordering of MT’s fleet of longterm test cars; these are the cars that the magazine borrows for a year, puts them into daily use, tracking fuel mileage, problem areas, and running costs, reporting the good, the bad, and the ugly in the magazine. Inasmuch as the ragtop body style and the Vista Blue color were new for 2008, and Shelby was looking for some press for this combo, they offered MT the use of just such a car for six months. I spec’d out the car with Shelby’s Vice President of Sales, Customer Service, and Fun Gary Patterson. He suggested we make this one “something a little special” by starting with a California Special, or GT/CS, which had a unique two-tone gray and black leather interior treatment, and slightly different front and rear fascias compared to the regular Mustang GT. He said they’d done a couple this way, which came out very well. So that’s how they built the MT car. It was completed in November 2007, and I flew to Shelby in Las Vegas to pick up our new baby and drive it back to Los Angeles.
The car performed admirably in the hands of the MT editorial team, logging about 10,000 miles during its six-month tenure in the MT garage. Even the younger staffers, usually more into Mitsubishi Evos and Subaru STis, liked it, even if they didn’t fully grasp the old-school muscle car thing. There were few problems save a faulty, rattling shock absorber, and massive noise issues with the rear axle, all fixed under warranty. When the loan to MT was up, I asked Shelby American its plans for the car. They said they planned to sell it. I bought it from Shelby American on Memorial Day weekend 2008.
I generally prefer to keep my cars factory stock, but felt I could do a few things of a bolt-on nature that would improve the looks and driving experience without sacrificing the car’s originality. And of course any and every piece that came off of it would be saved for reinstallation should I desire to take the car back to dead stock. The engine’s performance, reliability and fuel mileage suited me fine, so no superchargers or nitrous oxide here, thank you. I lamented that the Shelby-installed billet grille did away with the stock GT’s grille-mounted driving lights, and I always liked the look of the early ’67 G.T. 350 and 500 with its foglights mounted close together in the front grille. Latemodel Restoration had the answer in the form of a black, honeycomb-style grille that mimicked the look of the factory GT piece but without a running horse badge in the middle, and the original driving lights mounted up front and center. Shelby sent me a pair of N.O.S. driving lights and the factory wiring harness, and I swapped the grilles out, gaining the foglamps back, and a bit of an old-school ’67 Shelby vibe along with them.
The next few little details were small, in the form of a bright red starter push-button (replacing the cigarette lighter in the middle of the center stack on the instrument panel) and a black Hurst shifter ball, replacing the factory white ball. I also wanted to jazz up the engine bay a bit, without it looking like the car fell into a chrome plating tank. I found the little extra bit of bling I was looking for in the Shelby Performance Parts Catalog in the form of its billet aluminum accessory cap kit, which gives you a new set of racy, brushed billet aluminum caps for the radiator, power steering pump, oil filler, and windshield washer tank. Not expensive, and no hassle to install.
01. Wanting to make the most of the body style’s homage to the ’67 and ’68 Shelby Mustangs, I chose this aftermarket grille, which put the driving lights back on the car (as Shelby removed them for Shelby GT builds) that put the lights in the center resembling the early ’67 Shelby G.T. 350 look.
02. The ’08 GT came with Ford’s own 18-inch five-spoke wheels, which look nice but aren’t very wide. So I went for Ford Racing’s G.T. 500 spec alloys, which are still 18s but staggered and much wider all around. This allowed me to run more aggressive low-profile rolling stock, in this case Continental ContiTracs matching the sizes on a G.T. 500.
03. This bright red starter button seemed like a trick touch to me, and is actually a Honda part from the S2000 sports car; www.latemodelrestoration.com sells the whole kit with wiring for about $60, and it’s an easy install in place of the standard 12V accessory outlet (no juice worries though, as there’s another one in the console). This car’s Shelby serial number is 999, in honor of Henry Ford’s famous old racing car of the same name.
04. Shelby installed Hurst shifters on all manual trans Shelby GTs, and topped them with a white shifter ball, which looks very ’60s and fit fine. I changed mine to a black shift knob since there wasn’t another single piece of white plastic trim anywhere on the car or in the interior.
05. I wanted to make the engine compartment look a little more special and a little more Shelby without over-blinging it, which led me to this Shelby Performance Parts billet aluminum accessory cap kit. Some of the caps replace the existing factory caps, while others screw or clip over the factory pieces. No matter, install took about 15 minutes, and the pieces have a high-quality factory look about them.
Next order of business was wheels and tires; even though the factory-polished 18s looked great on the car, the tires weren’t very wide, and the Bridgestone all-weather compound wasn’t very sticky. I experimented with a couple of different sets of G.T. 500 wheels before settling on this set of wide 18 inchers from the Ford Racing catalog. They’re the same pieces you’ll find on a ’10-’12 Shelby G.T. 500 convertible running the same massive tires. The rears stuck out a little proud of the fenderwell, so I bolted on a set of those neat little factory black plastic mud flap extensions from the G.T. 500; inexpensive from the Ford dealership parts counter, and five minutes a side to bolt on.
The massive meats fixed one problem, and created another. Recall that part of the GT’s Shelbyfication includes a suspension upgrade from Ford Racing comprised of stiffer shocks, springs, and beefier antisway bars, which with the stock tires gave a nice balance of ride and handling response. But given my swap to much lower profile tires, the ride got pretty harsh and the convertible’s only so-so body rigidity was more compromised. So I struck out in search of more chassis/body rigidity and maybe some less racy suspension bits that would help to maintain good handling while suppling up the ride just a skosh.
My idea was to replace the Ford Racing springs and shocks, but not the antisway bars; again with the stock tires, the Ford Racing bits were fine, and might have worked better on a coupe given its more structurally rigid platform. I researched shock and spring rates until I was Ford Blue, and ultimately settled on ’07-’08 G.T. 500 pieces; beefier than stock Mustang GT units, but less aggressive than the racy Ford Racing hardware. Shelby just happened to have a brand-new set of take-offs handy from a recent G.T. 500 Super Snake conversion, so that’s what we settled on. Plus it was time for some serious weld-in subframe connectors. Any good shop could have handled all this, but I decided to bring the car back to Shelby American in Las Vegas, as they had all the parts in stock and certainly know the product. At Gary Patterson and Gary Davis’ recommendation, we also popped in a set of Maximum Motorsports fully adjustable front camber plates so the frontend could be more precisely aligned. And Shelby Performance Parts’ own adjustable Panhard bar to better locate the rearend during cornering. The job, plus a very precise alignment, took a day, and home I drove.
The improvements here proved massive; the car rode better on L.A.’s ruddily complected freeways, and I’ve not been able to identify any reduction in handling capability. The subframe connectors really tightened up the somewhat jiggly chassis structure, which may have done even more for the car than swapping the shocks and springs (the Ford Racing antisway bars were retained, since we all hate body roll). For that final added measure of chassis rigidity, I’ve since installed a Shelby Performance Parts aluminum rear shock tower brace, which mounts neatly in the trunk right at load-floor level so there’s no compromise in terms of luggage capacity. Galpin Auto Sports installed the bolt-in piece in minutes. There’s no need for one in the engine bay, as Shelby had already done the job when the car was built with a very neat Ford Racing front shock tower brace.
What’s next? Not much, just lots and lots of miles with the top down. Actually, a couple items remain on my to-do list. My car came without the optional center-mounted gauge cluster on the dash, which somewhat replicates the look of what Shelby installed on G.T. 350s in 1965-’66. I’ll probably have the Shelby American shop pop in a set of underdrive pulleys just to free up few more horsepower as well. I might throw a higher performance tune into the PCM while it’s at Shelby for the above too. All said and done I’ve added about $5,000 worth of upgrades that make the car feel more like a real Shelby Mustang, and a bit more unique at the same time.
06. Installing G.T. 500 rolling stock on my Shelby GT gave me a wider footprint, but I was concerned about rock chip damage on the lower rear quarters. I went for these factory Ford mini-mudflaps that Ford installs on the G.T. 500. They are a dealer order part and installed in predrilled holes in the fenders using existing screws.
07. Mustang convertibles suffer from a bit of chassis flex, so the Shelby American Mod Shop brewed up a custom cocktail of chassis improvements designed to eliminate the body wiggle. Most important was a set of weld-in subframe connectors that tie the various subframes to the center of the chassis.
08. They also recommended an adjustable Panhard bar to properly locate the rear axle side to side and keep it precisely in line at all times.
09. They also hooked me up with a rear trunk area shock tower brace that provides a little more structural rigidity in that area, complementing the engine bay strut tower brace that came with the car.
10. Finally, Shelby installed a set of Maximum Motorsports camber plates atop the strut towers, which allows for multiway and precise wheel alignment, so we could properly set camber, caster, and toe. The cowl shake and body wiggle is all but gone, and the steering response improved considerably; plus there’s a big improvement in ride quality and handling.