Back space help please!!

It's a B body Dana cut to A body specs , hence the 4.5 in bolt pattern.
OK, so I have an 8.75 with B-body backing plates and aftermarket axles.

My combination:
15x7 with a 5 inch back space and a P235/70R15.
CalTracs with 2 inch wide mono leafs.
Have run 15x8 Convo Pro with 4.75 back space and 2.5 inch wide Super Stock springs.
Did test fit a 15X7 with 4.25 back space and P255/60R15 = too close to stock outer wheel lips.


I think it's important to put the tire as close to the spring leaf as possible on these cars. The quarter panel/wheel lip is where you need clearance due to body roll. The leaf spring pretty much always remains in the same place.
20250415_193625 (480x640).jpg20250415_193902 (480x640).jpg