Street here is the jsut of things.
one if you want to lower just the rear, blocks is the cheapest way to go, it lowers the rear any amount you want, with 3 inches being about the lowest to go.
or a complete deal, springs in the front, blocks rear on RC's, a rear axle flip on QC's
this lowers the complete vehicle, ride suffers anytime you lower anything to a degree, but at the same time, handlling can improve.
Now to complete the lowering say of an RC, such as in my kit I supply new sway bar bushings, they are stiffer bushings than oem an provide a stiffer side to side movement in the sway bar, small , but noticable.
but when you lower something, you affect other things such as the sway bars, they are mounted to the frame and then on the front to the control arms, in the rear to the axle and the frame.
now when you lower the truck this oem angle changes, does it HAVE to be corrected? NO
to provide absolute best handling ? YES
you can do this by a number of ways, one is to cut the links and reweld, , another, have them cut an threaded for adjustment. third , buy Justins adjustable links.
but what these guys are talking about is aftermarket sway bars, they are usually a better bar than stock for better handling..
needed? NO, but they provide much bettter corner carving material for high speed purposes.
Now on to the jitteryness onthe highway, that comes alot from the stiff springs in the rear .
lowering it doent really afffect that much. the only thing to do there is either remove a couple of leaves, or have them rearched by a spring company. to soften the ride accordingly, but then it takes part of the handling away, it is them you must decide, ride comfort of a caddy or handle like a porshce