It will fit, but you probably do noit want it for one or two reasons.
First, it has the biscuit style engine mounts, rather than the captured spool type mounts. Okay, just use biscuits with an interlocking tab, like from Schumacher, oir later pickup trucks.
Secondly, and more important, the idler arm is of the older variety (and expensive) that is mounted on a stud. In '68, Mother started using a through bolted idler arm, so it is mounted in double shear. You won't have the flexing (or at least not as much) as in the earlier steering.
You could cut the idler mount bracket off the newer K-frame, build a jig to hold it in proper position and mate it to the '67 K-frame. Otherwise, the swap will work fine.
Mikey Bynum
