Mustang Spec+ Package

67 Mustang GT500 4


You’re here because you just inherited a Mustang. Or maybe you’re about to pick up a classic to work on with your kids. Maybe you’ve had a car sitting in the garage under a cover and you’d like to get it out again. Whatever the situation is, you have trouble trusting the car. It’s twitchy, it wanders around the highway, the drive is harsh, the steering a little vague – everything about the car just feels… off.

These are the types of complaints we’ve heard from countless Mustang owners, even those who have spent thousands on all new parts only to have the car feel worse than it did when they started. This is how those cars end up in the garage, covered and forgotten.

That’s why we built on Spec+ Package. It’s a group of parts, a recipe if you will, to help build confidence, control and trust in these old cars. Repeatedly tested and loved, our goal is to get you back on the road with a complete system that works together to deliver a feeling.

Now make no mistake, this is not our “base” package. It’s not a mixture of crappy parts we threw together to make something “affordable” and try to get you to upgrade. No, this kit is composed of some of the best parts we’ve been able to source for a vintage Mustang with a few of our own touches to enhance drivability, stability, and handling. It’s not a race car kit. We would not recommend this setup if your goal is to dominate the local track scene. But if your goal is to dominate the local winery scene, or feel comfortable cruising to and from the mountains, this is the one you’re after (though we have seen this kit pull 1.1Gs in the turns).

What’s in the Spec+ Package

Front Suspension

We begin addressing the front suspension by replacing the upper control arm with a tubular replacement that we build in house. We design these arms to be slightly offset which improves positive caster, and we replace the mounted balljoint with a screw-in type, allowing for quick and easy serviceability down the road. We also spent a great deal of time focusing on the shaft that mounts our upper arm, making design improvements to the bearings, mounting points, and stops.

On the upper arm we mount a typical rubber spring perch (rubber rocks, don’t let anyone tell you different) and install a set of Hyperco 600lb springs and a shock that we helped personally develop from Bilstein.

We replace the lower arm with a stock option from Moog because, quite simply, it’s the best one we’ve found. We also replace the strut rod bushings with new rubber pieces from Moog that allow the strut rod to do it’s job.

We tie it all together with our 1 1/8″ sway bar.

Rear Suspension

We know that leaf springs can flex side to side by as much as 2 inches. In a sharp turn (like when avoiding something in the road) they flex out and suddenly snap back. This feeling is hard to describe, other than “I don’t like that.” So our goal is to create stability, and a positive feeling in the rear of the car when you need it most.

We start with our proprietary leaf spring. Leaf springs get a bum rap, mostly because the ones on the market today are typically constructed of the lowest quality steel in a design that hasn’t been touched in 50+ years. So we went back to the drawing board and came up with a design that improves lateral control, minimizes wheel hop (even on high horsepower applications), and utilizes an unusual mix of bushings to improve ride quality. We then back this up with a set of Bilstein shocks. Simple and effective.

Power Steering

If you’ve ever tried parking one of these cars without power steering, you know just how essential it is. But finding the right combination of pieces is a daunting task. Our focus started with the proper steering geometry, a bunch of math that helps tell us engineers how natural the steering is going to feel. After all, it shouldn’t take 13 turns of the wheel to turn a corner, nor should it take half a turn to make a u-turn.

So we start by replacing the steering box with a high quality KBS unit with a 14:1 ratio. We back that up with a KRC Power Steering pump, the likes of which can be found on everything from street rods to race cars. From there we source quality replacement components: center link, tie rod adjusters, and inner and outer tie rods. Again, focusing on the best stock replacements we can find, not the ones from the discount bin.

One Optional Upgrade to Consider

Though not mandatory, we suggest upgrading your spindles. In 1970, Ford introduced a beefier wheel spindle that is easily adapted to the front of the earlier cars with variations of the same parts listed above. Not only does this give you a stronger unit to bolt your wheels and new disc brakes to, it allows you to use a DRP Bearing spacer. These spacers lock the bears in one place, eliminating wheel flex on the spindle, improving wheel spin, and allowing you to “lock down” the wheel bearings.

This option is not easy to upgrade to later on. The entire disc brake kit is different, the tie rods are different, etc. So we strongly encourage you to consider this upgrade when purchasing this package.


Front Suspension

  • MOD Upper Control Arms
  • 500lb Springs
  • Bilstein Front Shocks (Street Valving)
  • Rubber Spring Perches
  • Stock Replacement Lower Arms
  • 1 1/8″ Sway Bar
  • Replacement Strut Rod Bushings

Rear Suspension

  • MOD 1 Rear Suspension Kit


  • MOD 1 Power Steering Kit
  • Replacement Centerlink
  • Replacement Tie Rod Adjusters
  • Replacement Tie Rods (Inner and Outer)