Glad to see some people chiming in. I was worried I might be talking to myself in here.
To reply to a few comments/questions: When I was driving this car I was active on TCCoA, but as I got more into my Supercoupe, I pretty much moved over to SCCoA. I haven't posted on TCCoA in years, but still have an account if I need to ask questions.
I plan on keeping the automatic in this car. My SC is a 5-speed, and again, I don't need to try to build something identical. Besides, all my other cars have manual transmissions, and I don't think it's a bad idea to have one automatic in the flock.
A Coyote swap would be pretty cool, and there's a guy on SCCoA who's done just that with one of these cars. But that would be more work and a lot more money than this swap.
Getting back into the project: I've gone kind of nuts with weight reduction on my Supercoupe. It currently weighs about 3,370 pounds or so, which is very light by the standards of these cars. I've gone so far as to replace steel idler pulleys with plastic ones and gut the wiring harness for all the wires, switches, etc. I wasn't using anymore. I"m not going to do anything like that on this car, but I will go for some of the easy weight reduction.
That brings me to the rear suspension. I put some good parts on this car back in the day. I converted the rear drums to discs, added Koni shocks, Eibach springs and braided brake lines. The shocks appear a little rusty from sitting (if I have to replace them, I've got some old NLA Bilsteins that should be nearly as good).
What does that have to do with weight reduction? Well, one of the best ways to shave weight from these cars is to replace the cast iron lower control arms with aluminum Mark VIII arms. It's (mostly) a direct bolt-in, and saves a bit over 30 pounds. Below, the T-Bird arm is on the left, and the Mark arm is on the right:
The Mark came with factory air suspension, so it doesn't have a spring perch. I picked up a set of aluminum perches (used in conjunction with urethane spring isolators, not pictured) from my friend Bill at Supercoupe Performance. I also replaced the toe compensator link with new ones I had lying around.
A couple important notes about the Mark 8 arms: First, they don't use the same knuckle bolts as the T-Bird. If you grab a set of the Mark 8 arms, make sure you get the Torx knuckle bolts, too. Second: The Mark 8 arms only have one mounting tab per bolt (compare to the T-Bird arms earlier).
Why is that important? Because it makes it theoretically possible to rip the knuckles off the control arms. Look at this next pic. This is from my Supercoupe--it has Mark 8 control arms as well, and at the time, urethane knuckle bushings. After a couple (literally just 2-3) 1.6X 60-foot launches at the drag strip, the combination of traction and torque nearly ripped the knuckles right the berkeley off the bushings. A few more probably would have caused a serious, serious problem. I can't stress this enough: Do not use urethane knuckle bushings, Mark 8 control arms, and drag slicks together.
I've since replaced the knuckle bushings on my SC with delrin, and haven't had any problems since.