My car already has new springs and shock absorbers and is sitting on 14 x 7's. I am planning on upgrading the wheels in a year or two and want to lower the stance of my car by about 1 1/2 inches and was thinking about using lowering blocks or coil spring locks to do this. Has anyone used blocks in their Z? Are there any other ways of lowering a Z without replacing the springs?

Lowering blocks are for leaf springs. There is no 'good' way to lower a coil spring car without replacing the springs. You will also run into camber problems when you lower a Z but there are ways to correct that. Just don't use spring clips or heat or cut the springs.