They didn't, (11"), except pickups and I've no idea how that would fit up. If he wants a heavier clutch, he might drum up one of the oddball (and variously called) 10 7/8, 10.9 etc, were used in the 70 440-6 cars. These are a cover that fits a 10 1/2" bolt pattern, and the thing is scalloped to accomodate a "just under" 11" disc. Some of us tho, had troubles with those. The one in my old 440-6 gave me trouble. Would not release clean
Then there's dual disc