my buddy is running a steel driveshaft I do believe, locker/posi is same thing to me idk if my buddy has eaton or a Detroit one an he has 3.73 also an his truck runs like a mf its a cammed 6.0 with some juice...here is the link to his build thread
http://67-72chevytrucks.com/vboard/s...d.php?t=283326