Rear tire fitment with 3 inch relocate kit on 70 Dart

IF that backspace is right, the 12.5 section should fit, with an A-body 8 3/4. With a b-body 8 3/4, you would probably need more backspace.
I have some centerlines that were factory made for stock width rears, with a spring relocation. 10.5 wide, with 7.25 b.s.