As far as I know, all the S/C-type wheels were 7.5" and 9.5" wide. The backspacing of the 5-pin wheels is the same as the 6-pins when you include the thickness of the adapter. Bob Lacy at Vintage is familiar with
our specs.
When we use the Sunburst wheels (all 7.5" wide) in the back, we use extra-long control arms to widen the rear track for a better look. So, you must commit to your wheel width and offset if/when we build your rear suspension.