QA1's or rancho's

for the rear on a 4 inch drop, need links part numbers, anything that would help on getting these.

the truck is a 99 silverado extended cab, 2 wheel drive, has cal tracs, and belltech 4" drop shackles and hangers with belltech nitro drop shocks, need to figure out what i need for the rear, as the back end is to stiff and the weight transfer is not happening, i got 90/10's coming in to help out, need to figure out what i need for the rear!!!