Eary VS. Late A-body rear end widths

I fit a 17"x9" into mine. No modifications, stock 8 3/4 sbp axle, stock spring location, stock wheel well. The fit was made through proper backspacing and offset on a custom rim. I have a 1/4" on spring side and 1/4" on fender side. I think the tire is just under 11" wide. I don't have a straight on rear photo, this photo makes it look a bit pushed out but its just the angle. They are tucked in there very nice, with a great stance. The fronts are 17x8. All stock there too, Kelsey Hayes setup. PM me if you want more details.
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If my memory serves me right the face of the drum on a stock 8 3/4 rear measures pretty close to dead center of the leaf spring edge and the fender lip. Which makes sense for design purposes. My wheels had to be 5” backspace with 1/2” offset which is actually equal to a 4 1/2” backspace and centres a 9” wheel within the space available. (Wheel design affects offset as I recall)