From my understanding, you don't want to use anything other than oil or assembly lube on main studs. You have to torque them pretty good (80 ft lbs) and using something else may give you false readings.
If I were using main studs (instead of bolts), I would probably put some locktite on the threads that go into the block. I wouldn't use the "permanent" type of locktite, probably just the light-duty one. The nuts on top of the studs, I'm really not sure. I used stock main bolts, and I don't think I put any locktite on them. I do remember I put locktite on my rod cap studs before putting the nut on.