Lots in here about the SLS (search on that, hydropneumatic or self leveling). And, I recall that there was one forumite who made the jump to some sort of shock/spring setup. FWIW, leathermang has an old 300TD parts car that someone has retrofitted with Gabriel (I think) shocks. But, it's not a runner so there's no telling what kind of ride it had.
My opinion is that the best solution overall is to repair the SLS.
Nevertheless, here's some threads:
SLS 1
SLS 2