A later model 14 bolt. You'd have to fab some things up to make it fit.
A direct bolt-in would be a Dana 60. A few C20's had this rear. A guy with a Camper Special offered me one when I was in your boat a couple years ago. Since then, I've seen a couple at the boneyards here. It was a bit of a surprise as I'd only ever seen the Eaton rears. You'd have to replace the ring and pinion obviously. But at least you can get 'em for a 60.
-David
