I tried 295/50/15's on 15x8 Mopar steelies on my 72 Satellite recently and they were just a bit too close to the quarter to work. I do remember thinking that the tire would still work inside those wheelwells with a bit less than the factory 4 1/4" backspace those wheels have. I've seen more than one 71-2 Plymouth B-body with 295/50/15's in the back. I know they fit. Stretching them onto a 7" rim will look goofy though. 275's (50 or 60's) fit decently on a 7" rim, another popular combo for the rear on those cars. Anything narrower than 275 looks too small i think.

The fronts will fit a 255 easily. I've seen 265/50/15's on the front ov a 71 Roadrunner. Looked good. I forget what the wheel was though... it was stock however. My 72 Roadrunner had 255/60/15's all around and i remember thinking they looked small, no fitment issues at all... as in, more room for bigger front and back. That car had 15x7" rallyes.

Just for kicks i put my 15x8" steelies and 295's on the front ov that Satellite... looked way mean, but rubbed slightly on the upper fender lip. Not going to work, but a 275/50 would with the right rim.