You ARE asking about the SCCA/NASA, autocross type, solo against the clock [NOT wheel to wheel], rallycross, and NOT the all out, wheel to wheel, GRC/World Rallycross, correct?
I would think that IF the courses were
that rough, bumpy, and jump/compression laden, and their classing allows it, that one would use a long body/travel type coil over with A LOT of threaded adjustment on it, and some gravel rally, long coil over springs.
If they are in an almost no mods allowed stock type class, I guess they just use the stock springs/ride height with a decent travel replacement shock, and just grit it out?