Modified Mustangs & FordsHow To Chassis Suspension
Factory Five Racing IRS Conversion - Independent Thinking
Factory Five Racing IRS conversion for the 1962 Mercury Comet Wagon Project
There were a few unexpected issues we found during the install. One in particular is the upper-control-arm-to-subframe clearance; there isn't any. With the upper arm installed, it comes into contact with the subframe before ride height. To fix this, we simply notched the subframe using a piece of 4x5 square tubing. Another issue turned out to be the factory tolerances. The 1960s manufacturing processes were notorious for poor tolerances, and there were several areas that were not the same side to side on the wagon. In order to keep it tracking straight, we needed verifiable reference points on each side. In the end, we measured from several points on the car.
Depending on what vehicle the donor parts come from, you could end up with an open differential. We didn't know the specs of the 8.8 that we had, so we chose to rebuild it with parts from Randy's Ring and Pinion, adding a Yukon Sure-Grip LSD and a set of 3.73 gears. Those parts are not included in the project total, though, as they are not required for every swap.
Aside from the basic handtools, you will need a MIG welder, chop saw, reciprocating saw, and a plasma torch if you can get one. The plasma torch is really nice when working with some of the tight spots and thick metal, but you can do it without one. A lift is really helpful as well. We put the Comet on our Quality Lifts 4-post lift and the added headroom under the car made this project much easier than lying on the ground and dropping hot slag on your stomach.
One other note—with the cradle installed, fitting the center section is a tough task. There is a sweet spot on the passenger rear section of the cradle where the pumpkin can be rolled into the cradle. Keep that in mind for your swap. The 8.8 weighs about 80 pounds, so it takes four hands to move it around in this tight spot.
For the running gear, we picked up a set of Weld Racing S71 18s and 20s, wrapped in BF Goodrich G-Force Radial TA KDW rubber. The lightweight forged wheels look ridiculously good against the Comet body and the large open spokes provide ample cooling area for the brakes.
This swap will work on any early Mustang or Falcon platform, and the total price is less than any custom-fit IRS kit, ringing the register at $2,600 for the cradle and T-bird IRS components, we replaced the hub bearings and rotors for an additional $250, bringing the total to $2,850, under our $3,000 goal.
We spent about four days installing the cradle into the Comet, and the results could not be more impressive, on the ground, you can't tell the wagon has an IRS, and who would even think it would?