I will most likely have to take of the diff cover, there is not tag on the cover. I need to find out is the 3:08 an 8-1/2" or 9-1/2" crown and pinion. The rear end is a 10 bolt cover and the truck is a 1990
1/2 ton P.U. I am guessing the 8-1/2 is 1/2 ton 10 bolt and the 9-1/2 is the 12 bolt 3/4 ton