Put disc brakes on the front from a mid-late '70s 3/4 ton or 1 ton. They will have the larger studs. You were going to do that anyway weren't you.
I had the opposite problem. The discs from a '76 1 ton had studs larger than those on my original '67 Dana. Don't remember the size, but 1/2-20 sounds right. I didn't want to buy 32 new mag lug nuts and change the 16 rear studs. It was cheaper and faster to change only the 16 front studs while the hubs were still off.
