Rim Choice with Dr. Diff's 13" Brakes

In the back, what spec did you use for the width of the S-60? I can get backspace info but I need to know the width of the rear axle.
I'm getting ahead of myself with the rear wheels. I don't have the S-60 in my possession yet, so I can't provide measurements. Luckily, the old 7 1/4 is still under the car, so I can still roll it around the garage. It'll be a good look with 14" Cragars in the back and 18's in the front.

The other thing is if your springs are in the stock location or not. 275’s will fit with the springs in the stock location, 295’s will not on a lowered car without other modifications.
My springs are in the stock location, and I plan to leave them for now. I wasn't sure if 295's would squeeze in there or not. I was leaning toward 275's anyway because I like the idea of having the same size tire front and rear. Am I correct in assuming that the offsets will probably differ from the front?

For a Barracuda the additional concern would be the lower front corner of the fender
Do you think an 18x9 as opposed to a 9.5" will keep me out of the front fender? My car came with 245/60/14's + 4.5" of backspace and they rub so bad. I swear it makes me cringe every time I take a turn.