Mustangs Plus Spring and Handling kit is available for all ´64-1/2-´73 Mustangs. The kit as shown here sells for $479 and includes a 1-inch front anti-roll bar and a 3/4-inch rear anti-roll bar with the end link hardware, bushings and fasteners; a pair of front coil springs in either 620 or 720 in-lb ratings; a pair of Ford coil spring insulator pads (PN C4DZ-5415-A); a pair of performance rear leaf springs with factory-style replacement shackles; and a set of four KYB Gas-A-Just shock absorbers with all fasteners, bushings and hardware. Mustangs Plus also offers upgrades including a 11/8-inch front anti-roll bar (an additional $30) and five-leaf performance leaf springs (an additional $50).
Prior to beginning the project, we measured ride height at all four corners. Each of the front wheel openings was 27 inches from the ground. In the rear, the driver- and passenger-side wheel openings measured 27-1/4 and 27-1/2 inches, respectively.
Mark Sanchez of Advanced Engineering West allowed us to use his lift to make the job go more smoothly. With the car up in the air, we placed a transmission stand under one side of the axle, unloaded the spring and removed it.
After removing the existing shackles, the front of the spring was installed first and then lifted into position to the new shackles. Since they’re heavy, it is helpful to have a friend assist.
The original U-bolts and spring perch brackets are re-used because usually they’re fine. (Mustangs Plus has them if needed.) Once one side is completely installed, begin the process on the other side, and the axle will rotate if both sides are unfastened.
Jim’s Mustang did not come equipped with a rear anti-roll bar originally. The Mustangs Plus kit includes a rear anti-roll bar that requires only four holes be drilled into the rear subframe. Shown here is the correct mounting procedure of the rear anti-roll bar end links.
The U-shaped bracket is held in place with the longer of the four supplied U-bolts. These fit around the leaf spring on each side.
With the end links secured just to the point where the urethane bushings are deformed under compression, the anti-roll bar is lifted up to the rear subframe. Align the new D-shaped bushing and U-bracket with the subframe, and mark the position of the holes to be drilled on the subframe. Drill a pair of 3/8-inch holes as illustrated.
After the holes are drilled, fit the shorter U-bolts through the holes but put a nut on one end to prevent the U-bolt from being lost inside the subframe rail.
With the anti-roll bar secured in place, you may have some exhaust system clearance problems. An exhaust system was to be fit to the car later, so the existing system was dimpled after heating it up with an oxygen/acetylene torch.
The rear KYB Gas-A-Just shocks go on easily, but must first be compressed. Install the top of the shock first and then compress it to fit in the axle perch. After an initial test drive, Jim decided the shocks rode more firmly than he wanted. He contacted Mustangs Plus and exchanged them for a set of four KYB GR2 shocks.
The rather wimpy front anti-roll bar was replaced with a 1-inch bar that proved to offer additional roll stiffness without adding harsh ride characteristics. New hardware comes with the new bar, which installs in the stock location.
After removing the front coil spring shield from inside the front wheel opening, a Snap-on YA142A spring compressor was installed on the spring. With considerable elbow grease, the spring was compressed. Once safely loosened from its perch, the shock absorber was taken out from the bottom after the upper mounting bolts were removed.
With heavier gauge wire and a shorter length, it would appear that the new coil springs are far too short for use in Jim’s Mustang. The fact is that they installed easily, offered less bounding and came within 1/4-inch of the ride height measured prior to removing the stock components. These 720 in-lb coil springs are used in ´67-´73 applications while a 620 in-lb coil is used in ´641/2-´66 Mustangs. The 620 in-lb spring can be used in the later applications where the owner wants to reduce ride height by approximately 1 to 2 inches.
With KYB GR2 shocks chosen, the new coil spring was fitted. Now the coil spring shield can be reinstalled. Ride height was 1/4-inch higher up front.
There’s no doubt that an installed coil spring packs a lot of punch, even if it is nearly 30 years old, but with the proper tools and common sense, installing the springs can be safely accomplished at home.
We worked with Mustangs Plus to acquire its Spring and Handling kit for ´64-1/2-´73 Mustangs. Due to the fact that the suspension remained basically the same through the years, this particular installation on Jim Madden’s ´68 Mustang served as a good example of the items needed to pull off this upgrade/restoration.
While the parts shown here aren’t concours-correct, they do make your vintage Mustang much more livable in a real-world environment. Body roll is significantly reduced, and with higher rate springs and shocks, this upgrade can instill the confidence you desire from your Mustang.