What size Ubolts?

I'm replacing my 7 1/4 with an 8 3/4 rear. Just ordered leaf springs and shackles. Does anyone know what size diameter and length u-bolts I should need to properly mount the 8 3/4? Thanks, any help would be appreciated as I'm trying to get this 66 Barracuda off the rotisserie.

Jim
Are you still around Jim? This is James, the guy that sold you the Barracuda. Wanted to see how it turned out. Haven’t seen any posts past 2017.