These guys can make you some springs.
Eaton Springs It would be the more correct and safer way of lowering but, it's a bit expensive. This would get you lower and a nice ride. If you want a 3" drop, you may have to add a 1" lowering block as the springs alone will give you about 2". If you plan on keeping the truck for a while, might be worth it.
Lowering blocks create undue stress on the rear axle. Creates a torquing and twisting effect. I temporarily installed 3" lowering blocks on my Pontiac and it put a HEAVY arch in those old springs. I only drive it once a week and it's got a no torque 239ci. When I install a hopped up 292, I'm definitely getting new springs.
