It's a bolt on!
There's been a lot of discussion in the past about the virtues, difficulty, and expense of putting an IRS into an early Mustang. It's what Lee Iacocca had in mind, so the legend goes, so it seems desirable to put in an IRS.
Well, in fact, the suspension technology on the early Mustang is about as far along as horse drawn caraiges were in the 19th century. Hotchkis type leaf springs locating an axle. Simple, cheap, and pretty effective.
The Toyota Supra has the same track as an early Mustang, so it seems a natural. It turns out, it's more natural than I suspected. Not only does it have the same track, but the frame itself appears to be closely dimentioned (in this case, the root word "dimentia") to the Mustang. The frame also appears to have been designed with strength superior to that of the early Mustang.
The virtues of using this setup on my car are pretty obvious, since I already welded on the front of a Supra. If you want to IRS your own Mustang, this setup should work well with mild small block mills. Disk brakes, gas shocks, semi-trailing arm suspension, blessed by Lotus, even slightly wider wheel wells. And best of all... cheap. Real freakin' cheap!
Note: Captions are on top of photo renditions
This is what I cut from the Toyota. Note the cooling fins on the differential. Apparently they are very much needed. If you plan to road race this puppy, plan on installing an external cooler. New diffs can be had from the Toyota dealer, but they laugh at you and charge more than $800.00 for the piece. Save the one you have.
This will work out pretty well. I have a square Toyota frame peg, and a square hole in my Mustang.
Now let's hoist it up for a test fit. Hmmm... the frame needs to come up another two inches, and then even the wheel wells will match!
Here's the view from the trunk. Note that the frame extentions from the Supra (arrow) will need to be extended to the frame of the Mustang. I may replace the Mustang rear frame altogether. It's pretty flimsy.
Fills up the wheelwell nicely, eh, wot?