Here's the Heidts coilover...
Here's the Heidts coilover rear suspension setup installed and ready to go in our '68 fastback. Carrying PN RM-101, it's also available with a 9-inch axle housing under PN RM-101-H. We were able to do the installation in about two days, not including the three pieces that needed to be welded to the axle housing. The rest of the system is a true bolt-in installation. It does require holes to be drilled for installation of the various brackets. Note that the tailpipes have been removed; they will be reinstalled at a muffler shop to fit around the Panhard rod and coilovers.
There's no question that leaf-spring vintage Mustangs can be made to handle pretty well. With updates such as mid-eye leaf springs, performance shocks, and a rear antisway bar, cornering prowess can be raised to a respectable level.
But when you make the move to a three- or four-link system, which eliminates the leaf springs and adds a Panhard bar or a Watt's link along with coilover shocks, you've clearly moved into a different realm of suspension design and technology.
While there are several rear coilover suspension systems on the market for '65-'70 Mustangs and all have their unique design elements, two things they all offer are ride-height adjustability and better ride quality. There's no getting around the fact that a coilover suspension is going to improve the ride quality over a 40-year-old leaf-spring suspension. That's mainly due to the fact that to get a similar effect on handling improvement, the springs in a coilover system don't have to be as stiff as they do with leaf springs.
To quickly examine various designs on the market, you'll find the main players have a three-link with a torque arm as the third link; those setups usually include a Watt's link. Another design is a triangulated four-link that designers feel will work well without a Panhard bar or a Watt's link. A third school of thought is the system we're showing here. Offered by Heidts Hot Rod Shop, this arrangement is a straight four-link that also uses a Panhard bar. We stopped in at Reenmachine and watched our friend Pete Waydo install it on a customer's '68 fastback.
All three designs have merit and it's pretty much a matter of personal preference. In any case, a coilover design is worlds beyond what a leaf-spring setup offers. And we're sure many vintage Mustang owners will want to consider the previously mentioned attributes of better ride quality and the option to adjust ride height.
 This is the Heidts four-link...  This is the Heidts four-link setup as unpacked from the box. Everything is included. The major components are the adjustable coilover shocks and springs, chassis and axle brackets, long and short adjustable links, an upper coilover crossmember, a Panhard bar, and hardware. |  We separated these pieces...  We separated these pieces from the rest of the package to show what needs to be welded to the axlehousing. It's not a big deal and can be done by a good welding shop. The four-link brackets allow the links and the coilover shocks to be attached to the housing, while the single part is the axle mount for the Panhard bar. |  Before disassembly, our car...  Before disassembly, our car looked like this. There's nothing new here as we've been looking at leaf-spring rear suspensions on Mustangs since 1964, right? |
 Removing the rearend is fairly...  Removing the rearend is fairly basic. Remove the shocks, then disconnect and remove the driveshaft, brake lines, and emergency brake cables. With the rearend supported on jackstands, Reenmachine unbolted the leaf springs from the car. |  The car was simply raised...  The car was simply raised on the hoist to separate it from the rear axle. |  Using a cutoff wheel, the...  Using a cutoff wheel, the rear sections of the exhaust system are removed. You can either go with turndowns at the mufflers or have the tailpipes rerouted at a muffler shop. |