need insight to a-bodies

I was on Firm Feel Inc's website (firmfeel.com) and for k-members they show 63-66 as one, no listing for a '67, then a 68-72, finally a 73-76 listing. Moparts.com has a listing by part number for all the k-members. Basically the part numbers change every year and based on 6, smalll 8, and big 8. What it doesn't tell you is what changed. I can't imagine chrysler changed the k-members every year, so I am thinking it is only small stull like, bushings, torsion bar mounting holes, heck motor mounts for all I know. Since our rack and pinion kits mount to the k-frame, this seems like a logical place to begin.

Brian