I have been running 8" wide unilugs (Cragar SST's) for probably 15 years using 1/4" spacers to make 1/2" clearance between the sidewalls and springs. Here in PA your not allowed to run thicker than 1/4" spacers, check your local laws. The unilug nuts don't protrude all the way through the center of the wheel so there's nothing to line up between the spacer and lug nuts.
You can also cut off the bump stops from the frame, grind and weld (it is a three layer joing), and you get a lot of room that way, 1.5" or so.
I have run to 295 /50/15 American Racer tires. I have run 275 50 15 Nitto drag radials with weld wheels with three and a half inch backspace with no problem. No spacers