My Corvette(s): 1966 white roadster, "Plain Vanilla"
I have 195-75-15s on my car. The spare fits fine with standard bolts.
Here's a note from a post by johnz (below - under a gold line tire question)
I have Coker 205/75-15 redline radials on bolt-ons (same size as KO's) on my '67, and the spare fits fine in the tub with the "long" hanger bolts in the front and the stock hanger bolt at the rear. However, my upper tub is a repro, which is slightly larger in diameter than the original - the same tire won't quite fit in the original upper tub.