I did the Chevy spring swap using a 3 spring + overload pack and took the overload out so I have no problems with the e-brake cable. I didn't have to shim, my pinion angle was right on the money (about 2 degrees off in the rear, so while under power it should be perfectly parallel with the transfer case). There is no driveline vibration.

At first I used a double shackle setup, but after everyone got me worried about using double shackles I switched to a single shackle using the existing rear shackle hanger. The shackle is pretty laid back, but the truck rides fine and flexes good.