1hotdawg
+1y
Sway bars will help your handling the most. You could possibly, if lucky, find larger torsions...mine are sway a way that picked up from someone on here. I have even thought about fitting some QA1 coil over shocks in the control arms if it's possible and keeping the torsions allowing them to help each other out. I haven't measured yet to see if they'd work.
My personal plan for upgrading handling on my own drop is a front sway bar. I'd see how that helps out. Then possibly Beltech rear leaves and new rear bushings, (bushing upgrades will definitely help). Next would be a rear sway bar if I feel it needs it. And if the front needs more stiffening I'd try my QA1's if I see the measurements work. I have thought about running QA1's in the rear as well.
All that said, if you really want to handle 300+ hp, and not break things, you may want to look into bigger rearend modifications.