american racing Ansen Sprint Rims??????
15x8 with 4 1/2 backspace seems to be the golden choice for the rear on a lot of mopars, usually the biggest/best fit for the 66/67 b-bodies (i have a lot more experience with them) and they have the tightest wheelwells of the b's.
I personnaly much prefer too much backspace to too little. Too much can be fixed with a spacer, too little backspace and the tire rubs the fender, or won't even go on at all. I have a couple pairs of older one piece five spoke mags that i cant use for just that reason. The right size tire for the width of the rim wont clear the fender, too little backspace.
I'm currently using spacers on three of my cars, but they are all racers and use long studs with the spacers, nhra requirement.