Stan, Had a 510 for a few years down here in SEDIV. One of the first things we did wa to burn out the rubber rear subframe bushings and use metal bushings in place., Second was to slot the inner suspension arm mount. FOr the suspension, we used 300zx shocks in front, 510 in back (konis). Don't remember spring rates, but I think that the front springs were cut 300zx units. Watch you front spindles, they tend to bend if gator teeth are abused.