nasty vibrations

[dusterbd13]

after installing what are supposedly belltech 3 inch drop leaves in the back of my truck, i have come across a vibration in top gear, cruising, at speeds of 50 or greater. its bad enough that i can watch the bed rock in my side mirrorrs. i have just finished measuring angles, and now im unsure what to do with them.
i used an angle finder from lowes, and measured using a 3/4 short socket from the u-joint caps, with the cap being perfectly centered at the bottom of the driveshaft. the angles are:
front, yoke: +4
front, Drivehsft: -1
Rear yoke: +3
Rear driveshaft: -1

and as far as the numbers themselves are concerned, my math gets me to + 3 front, and +2 rear. if what im reading all over the place is right, i wnat to bring my rear down to -3, correct? equal but opposite? so that would mean 5 degree pinion shims.

am i way off base here?

Michael