Not sure on final tire size yet. Since it's going to be a street driver,my first thought is same size all around. But nothing is set in stone yet. It appears I could go bigger in the back if I want.
If the intent is to be able to rotate the tires, you need the same offset F/R as well. That won't necessarily let you max things out, but that may not be a big deal. In my particular situation, the 17x8 5.7"BS wheels do a good job of letting me run 245/45's on all 4 corners. With the perfect rear axle, that same wheel would fit a 275/40 on all 4, but the early B-body rear puts a 275 just a little too close to the outer wheelwell for real regular street action. Tolerable, but not ideal. Without relocating springs and maybe some minitubs, I think I'm maxed out at 275-285 in the rear.
IMHO, if you can't make the same wheel work on both ends, may as well go big/bigger.