68 kframe vs. 73 & up

I was hopeing to find a later K frame within a reasoable distance from home(oregon coast) my thinking was the spool type mounts and swaybar setup was better on the later K frames, I have also read that the Idler arm is somehow better. Is this all true I could really use some input on this subject from you guys in the know. I plan on tubular upper arms stiffening plates for the lowers to go along with the poly(graphite inpregnated)bushings and 1" torsion bars I already have, I have everything stripped already but don't really want to waste time with this 68 (Barracuda) K member unless It has some advantages over the later model. I plan for this car to handle so it will be getting torque boxes as well as frame connectors. Maybe I'm being rediculous but I want the best setup on a tight budget that I can get so a tubular k member is out of the question for now. thanks for any input I get