SCCA rules question about swapping parts between year models.

[djsilver]

I'm starting a project building a '90 coupe into an SCCA D-street prepared autocross car. The question I'll pose here is related to the "update/backdate" rule for this class. It basically says I can swap parts from any of the '89-'98 USDM 240's as long as the part came standard on some version. I can pick and chose from "option packages" and "groups". The only real limitation is that engines (read long-blocks, since intake and exhaust are open) must be swapped in whole (no mix-matching of internals from different years). I already have a '91 KA24DE engine that will go in. Intake & Exhaust manifolds, ECU's, springs, shocks, swaybars, bushings, wheels, differentials, clutches/flywheels are open so we don't need to consider them here. I can't use the bigger 300zx brakes so I don't see any advantage to go to the S14 5-lug setup. I'm thinking of things like entire subframes, suspension links, glass, dash frames or other items that were significantly better, lighter or missing entirely from certain models. Lowering the car is a certainty but are there differences in subframes/suspension pickup points that will suffer less from the change in roll-center, dynamic camber changes or bumpsteer that comes from lowering? Is the longer wheelbase of the S15 built into the subframes or the unibody and are there desireable combinations? The goal is to make it go/turn/stop better on an autocross course.Thanks, DJsilver