Agustin Jimenez
Technical Editor
May 26, 2017

The 5.0L Fox-body Mustang is often criticized as being a straight line car that can’t corner or stop… and what can we say? They’re not entirely wrong. The truth is these cars have been mopping the floor with the competition since the mid 80s but with modern cars getting ever faster, the stock Fox platform leaves a bit to be desired when it’s time to go. It’s easy to see why once you look at all the heavy components underneath. Take the K-member for instance: It’s big heavy and bulky and if you have aftermarket headers, it’s a real pain in the neck when replacing the starter motor. Our biggest problem with it is that it hinders weight transfer off-the-line at the track, resulting in mediocre 60-foot-times.

Luckily many aftermarket companies have stepped up to the plate over the years with stout solutions to lighten up the nose of the Fox Mustang. We decided early on that our 1991 Mustang was going to strictly be a track car, but we knew the stock components weren’t up to the demands of hard launches on sticky tires so we called up UPR Products and had them send us their Chromoly Tubular K-member and A-arm kit along with a set of Strange Engineering 10-way adjustable drag shocks, front coilover kit, a flaming river manual steering rack and pinion, torque box reinforcement kit, and of course their full Pro Series rear suspension.

We loaded up our Mustang with a trunk full of parts and headed over to Bocho Auto Repair in Montebello, California to turn our pony from shy to surefooted on the strip. Follow along as we show you the ins and outs of what it takes to trim the fat off your Fox-body Mustang and make it meaner, leaner and faster than ever before.

1. Here’s the complete UPR Pro Series rear suspension and front coilover suspension kit

2. The first order of business before removing the factory K-member was to disconnect the battery and support the weight of our engine with a fender brace. This allows you to unbolt the K-member from the undercarriage while still having a support for the weight of the engine.

3. Javier Jimenez, owner of Bocho Auto Repair, removed the motor mount retaining nuts and proceeded to remove the stock steering shaft, front calipers and rotors as well as the struts. With that out of the way, it’s as easy as hitting eight bolts with an air impact. Make sure you support the weight of the K-member with a jack to keep it from crushing you. We used a transmission jack to make the job easier.

4. This stuff really does add up and when you’re trying to get the best possible weight transfer to get the power to the ground, it’s easy to see why we opted to dump this in our scrap recycling in favor of something much more adequate for the task at hand.

5. The Chromoly K-member features a Silver Powder Coated finish, thick 0.250-inch motor mount pads as well as precision TIG welding. The biggest benefit other than generous amounts of clearance for headers, a large oil pan is how much lighter it is compared to stock. UPR Products tells us that it will shave 70 pounds off the nose of a Fox.

6. Say goodbye to the massive factory sway bar; we won’t be needing it to make some fast passes at the strip.

7. With the sway bar out of the way, we bolted in the K-member. Keep in mind that the factory locking nuts are reused to ease future removal/installs if needed.

8. With the K-member installed, we went ahead and installed a new Flaming River manual steering rack and pinion. Our car was originally equipped with a power steering pump and a previous owner thought it was a good idea to dump the pump and loop the lines. If you’ve ever driven a power steering equipped car with no assist, you know how difficult it can be to turn the wheel. The Flaming River manual steering rack and pinion is just what we needed to have a firm steering input while not having to hit the gym twice a day to drive our car. While it’s not a one finger operation, it’s definitely a significant upgrade over the previous setup we had; as long as the car is rolling a bit, turning the wheel feels pretty effortless.

9. Once the Rack and Pinion was installed, we put mocked together the Flaming River high-angle steering shaft so we could see how much we would have to trim the shaft down to fit our application.

10. You can clearly see here where the shaft needs to be shortened. It’s as simple as scribing the solid shaft and taking it over to your trusty chop saw to trim it down.

11. We went ahead and marked off exactly where each steering u-joint would sit and then proceeded to drill stud locators on each shaft where we needed them. Make sure you use a punch to keep your drill bit from walking on you while drilling on the new shaft.

12. With the shaft drilled, the set screws sit nice and tight in the shaft u-joint, which offers enough clearance for aftermarket headers.

13. We next turned our attention over to the lower control arms. The Chromoly K-member kit offers two different sets of bushings; one set is red while the other is black. The red bushings feature a higher Durometer rating, which means they’re a stiffer bushing. They’re great for a full on track car, but since our car would likely be driven to the track, we opted for the black bushings to cut down on vibration and stiffness for a more comfortable ride on the street. A word to the wise, the grease goes on the steel sleeve, not between the bushing and A-arm.

14. Don’t forget to install the Zerk fitting on the lower control arm ball joint.

15. The control arm slides right in without issue. Our control arms feature a sway bar mount in case we ever decide to install an aftermarket sway bar.

16. We opted to run a Strange Engineering 10-way adjustable strut up front along with a UPR Products coilover kit. These shocks allow you to dial in the rebound valving on the shock for hard and consistent launches at the strip as well as making quick, easy tweaks to control firmness and ride comfort with a simple turn of the knob.

17. The threaded aluminum sleeve drops right over the Strange Engineering 10-way adjustable strut.

18. With the threaded aluminum body and coil springs hardware in place, we reinstalled the supplied Strange Engineering dust covers to help keep out road grime.

19. It’s important to install the coilover top with the washers and flat needle bearing assembly in the correct order.

20. With the coil spring in place, we went ahead and dropped the coilover top cap in place.

21. Be sure to extend the strut’s shaft all the way out.

22. Place the caster/camber plate lower retainer up through the bottom of the shock tower.

23. The UPR Products' caster/camber plates feature a 1/2-inch thick T-7075 Aircraft billet aluminum adjuster as well as a TIG welded spherical bearing housing to make alignment changes a breeze.

24. The kit comes with Grade 8 hardware and fits together seamlessly.

25. Once we slid our coilovers in place, we turned our attention over to our steering. UPR Products sent us their Extreme Series Bumpsteer kit to give our Mustang a more precise steering feel.

26. The UPR Products Extreme Series Bumpsteer kit is made of high strength 7075 Aircraft Aluminum while the rest of the hardware consist of 4140 Chromoly construction to eliminate bumpsteer for good.

27. With the front of our Mustang wrapped up, we got to work on the backside of our ‘Stang by separating the rear axle from the body.

28. Once the rearend is out of the way, it’s as easy as unbolting the upper control arms and shocks from the car.

29. We’re not fans of doing things the hard way so we took our trusty air hammer and blasted our stock differential bushings out of the housing.

30. Unless you like galled up billet aluminum, you need one of these to install the UPR Products Billet Spherical Bearing bushings. This ball joint tool made quick work of driving in our new bushings without damaging them in the process.

31. A common weakness on all Fox platform Mustangs is the torque box area. Even in stock form, these cars have enough power to twist, warp and even break the floor pans and torque box area of the car. UPR Products recommended we install their Heavy Duty Upper and Lower Torque Box reinforcement kit in our Mustang to make sure we don’t have to deal with those issues further down the road; especially, considering the abuse a drag car typically sees.

32. The lower reinforcements slide through the openings on each side of the lower control arm mount.

33. Once inside you can rotate it for the proper orientation.

34. We bolted it in to ensure the plate would sit perfectly flush against the body and then welded it in place. The space is a bit tight so be careful not to burn through while maneuvering the tip of your MIG gun.

35. Once the lower reinforcement plates have been welded in, you have to remove the rear seat and drill through the four holes from the topside of the brace, and into the body in order to mount the upper reinforcement plates.

36. Next you’ll need to drill through the spot welds in the body using the lower half of the upper reinforcement as a guide. Once you’ve drilled out all four holes, all you have to do is install the top upper plate and drop the bolts in place.

37. Once you’ve wrapped up the torque box reinforcement kit, you can reinstall the rear seat.

38. The UPR Products Pro Series Chromoly Rear Suspension kit uses adjustable upper spring perches. Installation is fairly easy but you do have to cut part of the stock spring pocket off to weld in the heavy duty adjustable spring perch.

39. A set of welding clamps will hold the spring mount in place while you weld it into place. Make sure you clean up the area to be welded beforehand. We mocked it in place and took a flap wheel to the pocket and cleaned it up before we laid down a bead.

40. Again, take your time and weld it up without burning through the thin factory sheet metal. One thing to consider, however, is protecting the threads of the adjuster from weld spatter; soak a shop rag in water and wrap it around the treads or coat the threads with a bit of flux welding grease to keep the spatter from sticking.

41. The UPR Products Pro Series Anti-Roll Bar will not work with stock tailpipes and ours had been monkeyed with several times before, so we opted to cut the pipes after the mufflers and use turndowns instead

42. We cleaned up the inside of the frame right over the axle bumpstop pads to weld in the anti-roll bar.

43. Each of the bearing end mounts of the anti-roll bar is marked with the corresponding side they belong on.

44. Place the bar up between the frame with the bearing ends attached and clamp them in place.

45. Keep in mind that you will be welding near fuel lines and a fuel source so use a fireproof welding blanket or at the very least some new clean shop rags soaked in water to keep the area around your work surface quenched.

46. With the anti-roll bar welded in place, we installed our upper control arms and set them at the stock length as our baseline. We will be able to easily adjust pinion angle if need be once everything is in place.

47. The rear lower control arms feature 0.83-inch thick chromoly tubing construction with a TIG welded ends, heavy-duty heim joints and a high gloss Silver Powder Coated finish. The spherical bearings allow the suspension to cycle far quicker than a stock style rubber suspension in order to improve 60-foot times.

48. Again, we set the rear lower control arms the same length as the factory control arms for now.

49. We used a punch to persuade the lower control arm into place on the axle bracket.

50. With our rear suspension in place, we muscled our coil springs into position. We opted for a 12-inch tall spring with a 150-pound spring rate. The beauty of this kit is that it will fit well within many of the sanctioning body rules for stock location springs while allowing your to fully adjust your ride height as well as spring rate to suit your vehicle.

51. With our rear suspension wrapped up, we went ahead and bolted in the Strange Engineering 10-way adjustable rear shocks.