Overall width drum-to-drum is 60 7/8" and the perches are 45 1/2".

An E-body rear will bolt in, even with the 1/2" difference in perches, but the pinion angle (6°) is wrong; the '65-'69 C-body is a better choice, same overall dimensions with the correct 3° pinion angle.

I just put the C-body rear in my '57 Dodge and it fits perfectly.