I just was on the dyno today with a motor and 5W-30, clearances were in the standard .002-.0025 mains and .002 rods and I setup the oil pump for a max pressure of 60psi. That's all it did and when it was hot was 35-40psi at Idle. If you have the stock bottom end in there just run 5W-30 if your oil pressure is too high.

Bret