Johnny, I've ran into the same issue. Marsh did some for me and when I got them the backspacing wasn't what I asked for. When I called them they told me that was as much as they could put into a wheel.
Wish they would have told me that before they took my money... At least Capt. Thundar got some use out of them!
Buddy, (FlatCad, 38flattie) turned me onto a guy, but his name escapes me. He made my rears, and they were exactly what I wanted! I'll do some digging...