Tom Shaw
March 31, 2016
Contributers: Pete Geisler Photos By: Danielle Pandeline

We all know that we need to carefully check out the authenticity of any vintage Mustang we are about to buy. There’s a lot to know, and a lot of ways to get tricked and wind up paying too much for less of a car than we were supposed to get. And it may not be because the seller is trying to hoodwink us; many times the seller didn’t fully know what he had bought either.

As prices for our vintage Mustangs and Shelbys continue to climb, a thorough inspection of what we are spending our hard-earned dollars on is more important than ever. Pete Geisler of Orlando Mustang ( has restored his share of Mustangs and Shelbys and knows what’s required for an original, show-winning car. He has developed what he calls a Pre-Purchase Checklist, which helps a buyer with the critical steps of assessing a car’s originality.

“We are looking for original spot welds versus a panel that’s been replaced,” says Geisler. “The inner fenders are the most important part of the body on these rare cars because they have the VIN numbers. We also identify the original doors, door skins, quarter-panels, floorpans, hoods, and trunk lids. Next, we look at the mechanical components—engine, transmission, carburetor, distributor, fan, steering box—anything that has a date code. Whether we are looking at a complex and valuable Shelby or a six-cylinder car, the process of determining if the body is original is basically the same.”

This is a complicated subject, and rules, while helpful, do have exceptions. Some people want to know everything down to the small details. Others just want to know about the driveline. Therefore, this is not an exhaustive, step-by-step roadmap of how to check everything for ultimate authenticity, but rather a basic intro into things you check for to size up a vintage Mustang/Shelby.

One other thing: Geisler offers this service to his customers, but insists on seeing the car in person—he won’t do it over the phone or send his documents as a DIY deal.

Getting help when needed is another crucial step. “Whenever there are questions, we go to the Mustang Club of America or the Shelby American Automobile Club,” he says. So with the intro out of the way, let’s follow along as a professional looks at some key elements of originality.

01. Plenty of enthusiasts know a few things about how to check for originality, but when you are about to open your wallet for a big purchase like a Shelby Mustang, paying a seasoned expert to have a look is money well spent.

02. A professional appraisal should come with detailed paperwork showing the appraiser’s findings. Pete Geisler at Orlando Mustang has developed his own forms for recording the details of the cars he examines. “We also look for paperwork going back to the original owners,” he says.

03. Checking the engines’ major castings—block, heads, intake and exhaust manifolds—for date codes is a good start; beyond that, check for reproduction parts. This cast aluminum oil pan from a 1965 G.T. 350 has its original Shelby part number. Reproduction parts always differ from originals if you know what to look for.

04. Here is a date-code stamping from the OEM open-element air filter lid. This, too, is a time when a seasoned professional’s experience is a benefit. “I’ve only seen three different date codes on Hi-Po air cleaners,” says Geisler. The explanation: “They were made in huge batches.”

05. There are three different numbers to know on a Holley carb used as OEM equipment on a vintage Mustang or Shelby: the Ford or Shelby part number, the Holley List number, and the date code. This is a replacement Holley carb, so it does not have a Ford part number. The list number identifies the carb as a Holley for a 1965-1966 Cobra 289. Below that is the date code, 1801. It stands for the 180th day (June 29) of a year ending in 1, presumably 1971, although the carb is still in production so it could be something else. Geisler says that even as cores today, original 289 Hi-Po and Shelby carbs are $1,000-1,500.

06. With four decades of restoration and rust repair behind us, body panels are a huge issue when assessing originality. Like engine components, the panels were stamped with date codes. This trunk panel shows its date code, 1 30 2C, in the front passenger-side corner. Geisler advises that the rules for body date codes are different from engine casting date codes. He recommends comparing them to other cars built at the same plant during a similar time because they vary more than engine date codes.

07. Spot welds are another telltale clue to originality. Factory spot welds were done with industrial equipment of the day and have a different look than restoration work done with today’s equipment. Replacing body panels is sometimes necessary for rust repair, but it also opens up the possibility that VINs may have been tampered with somewhere along the way. Original is always better (as long as it isn’t rusty). “Inner fenders and quarter-panels are the biggest items,” says Geisler. “Inner fender aprons are a big deal when you’re talking about a $100,000 car. Other parts that can be bolted on have less effect on the value.”

08. Look closely at these original spot welds from the area in the trunk around the fuel tank. Geisler says, “We look for what we call a splash that forms during the spot welding. We have a hard time duplicating them. When a car has been restored and re-restored, and the engine compartment has been sprayed with heavy primers and fillers and sanded over and over, it gets harder to determine if those welds are original. Same goes for the welds on the quarter-panels and doorjambs.”

09. Floors, as we well know, are another area that is commonly replaced. Leaking weatherstrip, cowl, windshield, and roof drip rails are all points of Mustang design that, over time, allow water intrusion. Once inside, it goes to the floor and causes rust. A well-done replacement floorpan is better than a rusty floor, but a solid original, like these is a best-case scenario.

10. This close-up of an unrestored door shows the original factory spot welds on the door skin, and the textured surface of the door structure. This texture gets lost during restorations, as repainting fills in the low spots.

11. Shelbys, GTs, and Mustangs with four-barrel and High-Performance 289s all had dual exhaust. Dual exhaust cars had this extra plate reinforcing the floor in the rear seat area where the mufflers hung from. Notice the factory seam sealer and how the plate and the sealer all have the original factory paint. This is a key thing to help authenticate a legit car coded for an A or K for a four-barrel engine.

12. Shelbys were disc brake cars, and disc brake cars used Kelsey-Hayes calipers. The original calipers had the Kelsey-Hayes trademark, a stylized K-H (circled). Check for this when appraising a disc brake car. Originals are best. Even if they’re not working, they can be rebuilt.

13. The export brace, a one-piece strut connecting the shock towers with the firewall, was installed by the factory only on cars being exported out of the United States. Shelby saw the value in the stronger unibody and included them on his G.T. 350s. Export braces added after the car’s manufacture bolt to the cowl, but originals like this one bolt to a bracket installed on the cowl by the factory. It was then covered in sealer.

14. Even the safety glass has date codes, though it likely won’t be close to the car’s date of manufacture listed on the door tag. “Glass might be made a year in advance,” Pete advises. But it’s all part of an original car.

Diary of a Deception

Sometimes swapping a serial number is done to “save” a rust-bucket Mustang or a car that has been totaled in a collision. Other times it is done out of pure greed, to turn a lower-price Mustang into a high-priced one. Nobody wants to get stung. That’s why it is critical to have an appraisal by a qualified expert before you buy. Pete Geisler walks us through the discovery of a Mustang with something to hide.

Geisler says, “Recently I was looking at a GT Mustang—not a Shelby. All GTs came with factory dual exhaust, so the engine would have to be an A-code 289 4V or a K-code 289 High-Performance, not a C-code (289 2V) that would have had single exhaust.

“This GT had all the right parts: VIN stamped in the inner fender, and nice, original spot welds. But when I got the car on a lift and got to looking underneath, the reinforcing plates for the dual exhaust looked like they were kind of made up; they seemed too thick, full of bondo, while the rest of the floors were really clear, really nice, with beautiful, perfect spot welds. So I lowered the car back down off the lift and looked underneath the back seat. It was very obvious that dual exhaust reinforcing plates had been installed in the car.

“That sent me back to the serial numbers and looking at them closer. I put the car back on the lift, and when I looked at VIN from the bottom of the fenders, it was obvious. I could see an outline of where the inner fenders had been modified and new serial numbers had been welded in.

“So my report showed that that car had been modified from probably a C-code or T-code and changed to an A-code so that it could be represented as a GT. That affected the price significantly.”