I have done a lot of tires and wheels on the early Barracudas and Valiants. For a stock suspension and rear end. The 8" wheel is to wide unless your running a tire with nearly no sidewall bulge.
I would run a 15" X 7" with 4.5" Backspacing 255/60/15 Tire if it was me. That is about the best set up and biggest tire in my opinion.
You start mini tubing and moving leaf springs then anything is possible, but you need to measure and figure it all out. I will say if your staying with a stock width "A" body rear end, mini tub and moving the springs under the frame you would be looking for a 15" X 10" wheel with about 7.5" back spacing.
