The ’72 (and older) B-body K-frames look like:
There was a /6 version and a version for all V-8’s. A few differences over the years – mostly with the pitman arm and sway bar location.
The ’73 to ’81 B and R-body K-frames look like:
Mostly unchanged over the years – but where are three versions, /6, small and big block. The
rubber mounts for K-frame are different from FMJ’s are – but the solid replacements (iron, aluminum or urethane) are the same as FMJ. With that said, the solid mount locations are different than FMJ (fronts for FMJ are rear mounts for B/R and vice-versa).
Note: if someone wanted to modify a FMJ K-frame for big block install - the above picture is a good example of what modifications are needed. The mount locations (Left to Right) is the same - but front to rear locations as well as height locations are different (for both sides).
The ’73-81 B-body K-frame are not easy to change out (an all weekend long job)
There is another crossmember, mid car ('73-81) that is also rubber isolated for the torsion bars make contact. I don’t fully understand why to make the torsion bar crossmember rubber isolated (on the fixed end of bar).
The part marked Crossmember Rear Anchor (shaded) is mounted behind the Transmission Mounting Crossmember. When assembled - there is two separate crossmembers, one just in front of the other. The torsion bars go through holes made in the crossmember (not named in the picture) - and you can see the holes there.
The ’66-78 C-body K-frame is huge (and heavy). It is like a full car frame but cut in half (front half) then boxed in and reinforced – so it weighs twice/three times more. Solid (pickup) cab mounts can work for them – but not sure would actually help any/much. The only time to consider removal of a C-body K-frame is for a complete/through restoration – for K-frame removal is not for the faint of heart.
BudW