How much will lowering the rear cost me?

[Classic Heartbeat]

4-6 drop parts list. (assuming your ball joints, tie rod ends, and control arm bushings are in good condition)
Front
2 1/2" front disk brake conversion kit
2" front lowering coils
2" front lowering shocks
Rear
4" rear lowering coils
2" rear lowering blocks
"C" notch kit
super panhard bar kit
shock relocator kit
4" rear lowering shocks (because I haven't found 6")

2-4 drop parts list depends on if you want to go front disk brakes or not.
if front disk brakes then all you need for the front is a disk brake conversion kit with 2 1/2" lowering spindles.
if not changing to disk, then what you need is 2" front lowering coils and 2" front lowering shocks.
Rear
4" rear lowering coils
4" rear lowering shocks
you may get away with just an adjustible panhard bar and not need the shock relocator kit or super panhard bar kit.
I would lower it and look at it to make that judgement.
WES