When I had the SB, I used Carrera shocks and springs. Springs were 375# all around, and I mounted the shocks upside down for less unsprung weight. Also, the fronts were 10", I went to 7" for more adjustability in ride height. Changed swaybar bushings and mounts F & B with polyurethane, greasable bushes on the mounts. The difference in handling and ride was night and day.
My current BB (but now with 17" wheels) has QA1s with 450# springs, again 10". With the shocks adjusted halfway, the ride scrambled my brains. I have bought 450# 7" Carrera springs for the fronts, still trying to find out if the shocks can be mounted upside down. With the shocks now at 2 clicks, the ride is much better; we'll see also after doing the poly swaybar bushings and mounts mod.
So I believe the current thinking for street is lighter springs, with a highly-progressive rate (not stiffer) shocks, will give a firm but smooth ride. The softer spring rate will allow the wheel assembly to move easier, with the initial compression of the shock going with it. Then, as the assembly nears maximum compression, the shock gets progressively stiffer, preventing bottoming out. Ideally, the rebound rate should be softer and more linear, so the assembly drops down to it's initial setting faster, preventing bounce. Won't work for the track, though.
