New '72 Demon owner here.

Welcome to FABO, i love the car!
The second A-Body i ever owned was a '71 Demon 318 3 speed on the floor with an 8 3/4 rear end like yours in 1981.
it is an awesome combination and a great package IMHO.
I had a lot of fun with that car and it never let me down.
I would love to see more pictures when you get the resizing thing figured out, and maybe start a build thread on here.
Also, I have another '71 Demon 318 that i plan on resurrecting in the future to replicate my old one, but it is an automatic and a Sizzler............