15x7 on BBody 83/4 - Anyone run this?

Looking for anyone who has performed a swap of a B Body 83/4 into an A body and runs the 15X7 BBP factory rims. I have been reading that early B Body rears (between 64-68) will mount up on the A Bodies with maybe just a spring perch relocate. The rear overall will be longer but can be used if proper backspacing is used. I have Wheel Vintique 15x7's with the 70R14 redlines I am using on my 68 Dart, and I believe they are 4 1/4 backspacing. Does any run something similar? Will the tires fit the longer rear? Thanks.