The weak links in the rear factory 4-link are the
control arms. Getting rid of the factory lowers with the squishy rubber bushings is the first step. If you replace them with lowers that have spherical bearings at one end e.g. MM, that'll reduce
suspension bind and make cornering more predictable. You might even be able to get rid of the quad shocks at this point and still not have wheel hop upon launch.
You then could do coilovers and reduce unsprung weight but that doesn't address the real weakness which is now the factory uppers. The question then becomes what to do next? You could do:
1. Adjustable uppers with spherical bearings at the axle end e.g. Edelbrock as I did. You'd still have a 4-link but these will further reduce
suspension bind and reduce lateral axle movement. Handling becomes more predictable with improved grip exiting corners and less risk of snap oversteer. You can also adjust pinion angle. A simple, cheap fix but there's better.
2. Watt link. You can do away with the
upper control arms altogether and you now effectively have a 3-link. Excellent, neat, but you'll need a side exit exhaust 'cause there's no room for tailpipes.
3. Torque arm/
Panhard bar. Also effectively a 3-link set-up, also excellent, but requires subframe connectors with crossmember to mount front end of torque arm. Adds a lot of weight, reduces ground clearance, and you need to modify the midpipe for clearance.
4. Steeda 5-link. A neat idea really. With the
upper control arms now parallel to the lowers to control axle rotation and a
panhard bar to prevent lateral movement.