It's easy to visually spot a 67 bayonet style idler. Only one tab coming off the K.
The 68 and newer use double shear mounting with a top and bottom plate coming off the K member.
With the A-body migrating from economy car in 1960 to a bigger sometimes performance car, they made things right. (Too bad they didn't go to the Big Bolt Pattern in 67)
Maybe
@mosleyme will be kind enough to help you out. He's in Plano.
