Hey guys do you think 70 b body to 72 e body rear swap is possible without changing wheel backspacing?I believe there is only slightly more than 1" difference in length.who know exactly or has ever done something like this before.thx in advance.

The spring perch centers are 2" different.

I did it years ago by using Dr. Diff's 1" offset kit.

It was a bolt in deal.

Nice and thx for the info didn't know they offered such a kit.....what about overall length and wheel spacing?thats my biggest concern.

Guess that depends on how much clearance you have now. Those old Mopar bodies had a lot of allowable body tolerances from car to car going down the same assembly line. I'd measure the clearance you have now, and subtract the difference from your current clearance. Back in the old days, you waned at least 3/4" clearance between the widest point on the tire to the closest point on the body, inside and out.

and don't forget to measure both sides.
it is very common to find 1/2" difference in the tub width to quarter panel, right and left.
also check drum mounting surface to spring edge. that distance can be different as well.
these measurements pertain to cars that haven't been crashed. if crash [or rust] repaired, these points of measurement can be better or worse, depending on the skills of the person doing the repair[s].

The early (pre 1971) B body 8 3/4 rear ends are 2.0 inches narrower than the 1970 and up E body 8 3/4, as already mentioned the E body leaf spring are not the same width as the early (pre 1971) B bodies are.
E body leaf springs are angle from the front eye to the rear shackle also
As far as the offset on the wheels and reusing those wheels and same size tires make sure they will have sufficient clearances on the inside, especially on the front inside to the leaf springs

ok guys thx