You have a long way to go. But a plan is nice... all my plans change half way through so I'm a bad example.

Doing it all original is nice but get tedious in less that is really your jam. It is a labor of love.

My 2 cents... make it run and drive well. A new built sub frame saves a lot of time and it will turn and stop like a champ. Build whatever motor you have to whatever makes you happy. Put a color on it that brings you joy. Personally I like an interior to feel like an old car.
Do that original. Except the tunes of course. That's a car you will never be afraid to drive, do a burn out, enjoy.

These days a numbers matching drive train is pretty much "numbers matching". Trans Am clones are well... clones. But if you like the spoiler... hell its your car.