'57 rear axle and rims with Porterbuilt.

[thotfulspot]

I'm finally starting my '57 stepside rebuild. I'm going to use Porterbuilt dropmembers, LS motor, 4L80E, 9", all the fun stuff. I'm starting with the bottom. The issue (the first one at least) is setting it up as a rolling chassis. The previous owner was running it without a bed. He put the widest rims he could find, probably 16", and some unknown rear end. We've got the rest of the sheet metal off.

I'm trying to figure out what the dimensions in the rear should be.
What I'm looking for is the width of the rearend and the offset/backspacing of the wheels. I'd like to use a set of Delmo rims. Unfortunately Del or Porterbuilt hasn't kept much information on builds. I'm looking for a setup like the Heisenberg. Del thought the width of the 9" housing was 57" or 59". The stock width is 58" from brake backing plate to brake backing plate. I'll be using discs. Has anyone here done the full Porterbuilt and Delmo build? If I had one of the measurements, I could probably work it backwards.

Any help is appreciated.