Thanks for the lead. Just got off the phone and we are hooked up. Let you all know the outcome. He said Bbody to Abody backing plates ok. Does this all day long. The other way around is a problem.
Right, you can use the big bolt pattern backing plates on an A-body, but ONLY if you use BBP axles. You can't use the B-body backing plates with the stock SBP A-body axles, because the axle flange offset it different on the SBP axles compared to the BBP axles.
