[Classic Heartbeat]

I just installed a set of (McGauhey's) 4" rear drop springs on a 70 2WD Blazer and the ride is smooth as a babies butt. However I also used lowering shocks, shock relocation kit, and adjustible panhard bar.
Your stock height shocks are probably close to being bottomed out. So even though they are swinging more than they are compressing, they are still bottoming out. Like others have said, you need a shock relocator kit and a set of 4" drop shocks. I would also step up and buy an adjustible panhard bar. It won't improve the quality of the ride, but it will allow you to recenter the rear end. The result of which will save your tires and improve the handling. WES