Street A bodies with springs moved into the rails

My car had the springs moved into the rails (front) but work halted and I bought the car. The front boxes are flush with the outter frame rail and stick out on the inside. If yours is set up the same way what is your axle width drum to drum and what is the perch to perch measurement? I just picked up a narrowed 8 3/4 that is 54 1/4 wide out of a Chevy Vega and need to figure out if this width is ok before I start hacking the Vega brackets off.
mopar_axle_sizes.jpg