The section width would be 8.45". Checking the spec guides, a 5.5" wheel would be better, 6" for best performance.
What year/size truck are they going on? It sounds odd to me that a tire that small would have clearance issues, as most GM trucks from the late 40s to '72 should be able to clear a 11.5" tire in the rear without issue, and I've even mounted some 12.5" tires on a few without rubbing.
