Patrick Hill Associate Editor
November 28, 2007
Inside the body of this '91 Fox coupe beats the heart and soul of an '04 Mach 1. Using nothing but salvage Mustang parts and their own ingenuity, the guys at MPS built this car in three weeks.

Horse Sense: With today's Mustang aftermarket industry, almost anything can be done with a Fox-body car. From using later-model Mustang parts to modernize an older body to performing the full-on Fox-Rod treatment, anything is possible. Add to that the ever-increasing supply of late-model Mustang salvage parts and making a Pony unique from the rest only requires some imagination and a few phone calls.

For car guys, something simply being possible is usually the only excuse needed for a major project. In the past couple of years, installing modular motors into Fox cars has become more popular than ever. This is made easier with aftermarket bolt-on K-members, which reduce the amount of fabrication for the installs, and modular motors putting out decent horsepower numbers, even without a power adder. Add to that the plentiful supply of salvage motors and drivetrain pieces available, and mod-motor Fox swaps are on the way to being as common as 347 strokers.

Essentially the original Cobra motor dating back to 1996, the Mach 1's Four-Valve engine is a high-revving screamer that can easily motivate the lightweight Fox coupe to near light speed. Looking at this picture, you can believe that the entire front subframe assembly from the Mach 1 nearly bolted right up to the Fox body. Only a few simple modifications and the front end was secured.

Several companies specialize in salvaging Mustangs and their parts to keep other cars going and provide needed items for restomod-style projects. Wrecked Mustangs are picked clean of any useable parts and the carcasses are sent away to the scrapper. One such company is MPS Auto Salvage (www.mpsautosalvage.com). Based in Winder, Georgia, MPS (formerly Mustang Parts Specialties) specializes in wrecked and discarded Mustangs. The company either rebuilds them into driveable cars or rummages through parts from the wrecks to keep other Mustangs going.

MPS owner Greg Brittingham started the business 20 years ago out of his home garage, gathering Mustang parts and pieces to peddle at swap meets. When he began buying cars to part out, his side job outgrew his home garage. From there, he invested in a property for the whole operation with enough room to expand his purchase of Mustang wrecks and parts cars to feed his parts stock. Now the company even handles late-model drivetrain installs into early-model Mustangs and other Fords.

One day, Greg and Mark McDonald, MPS installation tech, were discussing what to do with a '91 Fox coupe they had at the shop. The original idea was to build a pushrod motor to install in the car along with a five-speed trans. Deciding the plan was too mundane for the coupe, they hashed over ideas for about half an hour. Remembering the wrecked '04 Mach 1 on the MPS lot, a light bulb went off in the guys' heads. Work then began on transplanting the Mach 1 motor and automatic transmission into the '91. Using nothing but salvage parts they had on hand and their own fabrication skills, the guys at MPS began building their Mach Fox. This will probably be one of the few times you'll read about an original stick Fox Mustang being converted to an automatic.

Putting the Mach 1 Four-Valve 4.6's power to the pavement is an IRS rear system from an '03 Cobra. After modifying the '91's framerails, the IRS slipped right in. Greg wants to give special thanks to Mark McDonald and DeWayne Stiles for their hard work to finish this project so well and so quickly.

But installing the Mach 1's engine and trans wasn't enough. Greg and crew took its whole front-subframe assembly and bolted it underneath the '91. According to Greg, all it took was a slight modification to install the front suspension. Without the mods, it almost bolted right into the Fox coupe. Using the '04's gear also allowed use of the '04 K-member that was already mated to the Mach 1's Four-Valve 4.6 V-8. Another benefit of using the '04 unit included the Mach 1's better brakes and five-lug rotors.

After the front subassembly was installed, Greg and crew put in the IRS rear suspension system from an '03 Cobra to give the '91 better handling. The rear framerails were modified to accept the Cobra IRS rear. After some other minor mods, the '03 Cobra rear found a new home.

On the inside, this '91 coupe is just as unique. The instrument cluster; front seats; '04 steering wheel (with airbag), power window controls, and shifter were installed to refresh the Fox's interior with a modern flavor. To install the auto shifter properly, the '91's transmission hump was cut and grafted from the '04's.

Wiring the Fox for a Mach 1 motor was no easy task, but Mark met the challenge head on. As the installation tech for MPS, he has a lot of experience when it comes to transplanting late-model engines into older Mustangs. He took the original Fox Mustang wiring harness and spread it out next to the stock Mach 1 harness. Mark spent 50 hours removing all the unnecessary wiring and accessories; then taking the needed parts from the original '91 and grafting them into the Mach 1 harness. He didn't do this by splicing, but the wires went pin-by-pin into the '04's plugs. By the end of the process, Mark produced one wiring harness that allowed everything installed from the Mach 1 onto the '91 to work flawlessly without a hodgepodge wiring mess in the car. Even the '04 airbag is fully functional with the '91 airbag control mechanism.

Once the car was mechanically finished, it went to DeWayne Stiles Paintworks in Winder for the spray work. DeWayne sprayed the '91 in its new hue of Satin Silver, finishing off the car's refit into this tire scorcher.

This Fox Rod isn't a trailer-queen show car, either. The '91 is driven by Greg every day to work, lunch, car shows, and local swap meets. From the outside, the only thing hinting at this car's secret identity are the '07 GT wheels.

5.0 Tech specs
ENGINE AND DRIVETRAINELECTRONICS
BlockEngine Management
'04 Mach 1Mach 1
DisplacementIgnition
4.6, 281ciMach 1
BoreGauges
3.55-inMach 1
Stroke 
3.54-inSUSPENSION AND CHASSIS
Cylinder HeadsFront Suspension
Mach 1 Four-ValveK-member
CrankshaftMach 1
Mach 1A-arms
Compression RatioMach 1
10:1Struts
CamshaftsBilstein
Mach 1Wheels
Intake Manifold'07 GT 17 Premium
Mach 1Tires
Throttle Body235/55/ZR17 Pirelli P Zero Nero tires
Mach 1Brakes
Power Adder13-in Mach 1
NoneRear Suspension
ExhaustSprings
04 Mach 1 headers, custom'03 Cobra
MPS H-pipe, '03 Cobra mufflersShocks
and tailpipesBilstein
Fuel SystemWheels
Mach 1'07 GT 17 Premium
TransmissionTires
'04 Mach 1 4R70W automatic235/55/ZR17 Pirelli P Zero Nero tires
RearendBrakes
03 Cobra w/31-spline Traction-Lok,11.65-in Cobra
4.10 gears