Bad Rattle!!!

[Radman]

Guys, I'm going nuts over this problem.. I have a lowered 68 chev short box with dropped springs in the rear. as i am driving i can hear a rattle in the rear of the truck, It almost sounds like washers rattling on a bolt or like a chain dragging on the ground. I have checked every nut and bolt under that truck at least 10 times and cannot seem to find it!!! what the heck am i missing????? I have even pulled the drums off and checked for anything broken or pads that are rubbing and every thing looks great. any ideas????