The rear control arms are integral ingredient of the car's suspension geometry. The lowers are especially key as they provide the lower mounting point for the rear springs, and also the rear sway bar. The reason the stock arms suck is that they are made of a cheap stamped u-shaped metal that flexes unbelievably bad. The uppers are not as important ... HOWEVER, the uppers are not that expensive and easy to change, so you might as well do them, too. The type you get has a lot to with your application. Drag racers are looking alot at the type that get you the best weight transfer and hooking of the rear tires ... I can not help you with any suggestions there. My car is purely a motivated street car, so adjustability is not a requirement for either upper or lowers. But I did opt ... and I am R E A L L Y glad I did ... for adjustable "weight jacker" type lowers to allow some tweaking of the rear ride height. As my springs have settled, this has turned out to be a nice feature. The handling difference after the new arms is extraordinary, especially when tied to a new heavier rear sway bar -- as the LCA's are the mounting points for the sway bar, the handling improvements are ... in my experience ... pretty dramatic. I really love my car's handling ... it is a lot of fun in twisty roads.
Regarding sub-frame connectors ... yep, get them and get them now. They are critical upgrade required for our aged chaisis. The car should come stock with them.
