lowering 3/4 ton?

[3/4 ton frustration]

I have a '71 GMC 3/4 ton that I would like to lower without breaking the bank. It's a 350, 4spd, Dana 60 (8-lug of course). At the moment I'm more concerned about lowering the rear WITHOUT doing an axle over the leaf spring. I would like to do a 2/4 drop. The cheapest route I wanted to take was to get longer rear shackles but cannot find anyplace to get them. Does anybody know where I might be able to find 3/4 ton lowering parts (especially the shackle)? The front I was thinking a shorter coil spring. I'm trying to keep the 8 lug pattern to avoid having to change the rearend. Any help or advice would be appreciated.