i put in a hyperflex bushing/body mount kit by energy suspension, and that stiffened the car up quite a bit. that requires a rebuild of the front and rear suspensions and is quite time consuming but definetly worth the effort.
i also put in a swaybar in the front (stock size) and urethane bushings.
sybframe connectors will also help out alot, do them when you do the rear suspension, so you dont have to do undo the springs twice.
i've got my connectors in my room, until my brothers car removes itself from the garage (we're swapping trans).