Assuming it's like the older ones, they're sorta weird bolts. My '74 uses a 1310 double-cardan (aka CV, i.e. two U-joints in one) at that end. The CV attaches with what look like 5/16" fine threaded bolts, maybe 1.25" long ... BUT they need a tiny head as they're a royal bloody pain to get at in there. Your standard off-the-shelf bolt will have too large a hex head, I think, to get a socket or wrench on whilst in place.
I'm thinking you gotta hit up your local driveline shop, or maybe a specialty fastener place (Fastenal, Grainger, whatever).
Or I could be totally wrong 'cuz you have a different t-case than me.
-- A