I need to set my rear pinion angle. I'm making custom perches out of 2-1/2 x 1/4 wall square tubing to get about 1/2" extra lift and fix the screwy way my spring pins wont sit in the stock perch. So I need to find the proper pinion angle to take the vibration out. I'm running stock springs and a shackle flip so I know i'm going to need some sort of compensation anyway. I'm not lowering my tcase, and there's no cv in the rear shaft. So how do I determine proper angle and then measure it?

bolt the axle under the truck with the pads not welded and let the truck down on the wheels. rotate the pinion up and down until the u-joint angles at each end of the shaft match. Once you have the angles matched, tack the pads in place and measure again. If they stayed, take the axle out of the truck and finish the welds

This explains angles a little bit (http://www.off-road.com/chevy/reviews/highangle/)