Ok I have a 56 mercury with a 390 FE the car was lowered at the rear 6" off the ground. I bought some springs from the junk yard from a caddilac, and cut them a good 6" or two rows. The suspension is really good, I am so suprised on how they turned out! It's better then the back suspension which is a few leafs and a lowering block. So go ahead and do it, and have fun with it too, just make sure you have good shocks in the front.

Kevin