I agree with MORSNOW on your having a front Anti-sway bar. I disagree that it is not needed in the rear. I am of the belief, any SRW will have a very notable improvement in sway reduction with anti-swab bars front and rear.
From what I have read, of the big three the GMs have the most flexible of the frames. My understanding is this is the major reason for the softer ride in the GMs.
In my opinion a stiff or flexible frame is not the major cause of sway. I believe it is in the suspension and center of gravity as it pertains to axle/wheel width. The stiffer the suspension and wider the rear tires/axles, the less sway.