65 Barracuda Fromula S - what to do

I'd get it running good mechanically and drive the crap out of it, then take it from there. Thats what I'm doing right now with mine, shaking it down. I find the 273 just fine (keeps me out of trouble), and the 904 shifts surprisingly well.

I personally wouldn't replace a good working transmission and rear if you are sticking to the 273/318. I'm a "if it ain't broke don't fix it guy", but that's just me. When the 273 craps out though its 318 time for sure.

I'm not sure what it's worth, but it looks like a clean car, good luck.