Dad has managed to get the 65 B Body 8 3/4 back in with new axles from Dr Diff and the Wilwood brakes on.
We flipped the front spring hangers upside down and moved them back 3/4". The rear of the springs have sliders rather than shackles.
The 15x7 steel wheels I have on in the pics are 4 1/4" back space but the 27.5" tires have a very wide section width compared to the tread. (9 1/2" section width...6" tread...7" wheel)I didn't really trust them for an accurate back space due to the increased section width as it relates to the tires position to the leaf springs.