/6 K-Frame vs. V8 K
EDIT, LOL I was typing as Okla was posting
The only suspension differences I know of are...........
The 67 only K has a single year idler mount, but you could fab that one to take later Idlers
The 73/ later K's run the factory sway far through the middle of the K, so a couple inches more clearance and a cleaner look.