12 bolt/Wheel Question

[10 inch tires]

I did a search and came up with nothing and i also looked at the sticky for wheel backspace and nothing again.

Anyone running a early 12 bolt (64-67) with notched frame rails?

I plan on running this exact set up in my 79 Malibu and was wondering what backspace i need with a 15x10 wheel. I am a few months away from installing the rear end, and reason i am asking is i found a set of wheels for sale and was wondering if they will fit. They are 5.5 backspace.

 

[ILLEGAL REGAL]

I ran that rear, 54.5" wide housing with a 9" wheel and 5-7/8"bs with the frame notched to the seam and they fit perfect with a 28-10.5

for room, I had maybe 3/4" to the frame and with the lip rolled had about 3/8" to the 1/4 panel