I installed a rear from a 1970 newyorker in a 38 Plymouth coupe once[it was cheap.......free ]. the tire/wheel combo used was a 15x6 chrome gm ralley type with the 10 bolt multi pattern and L78 tires which measured somewhere around 29.5 tall & 7 1/2" wide. I don't remember the backspace of the wheels, but that combo was very tight in the fender, but it had no rubbing. there was a bunch of room from the springs to the inner tire sidewall tho. a B body rear would have been a much better choice. now with that being said, my Hollander states the axles and differential parts interchange on plymouth from 37-48, so this should give you an idea of what could work for you.