Modification of K-member idler arm mount advice

So not to hijack but cn the earlier 66 k frame be converted to the double shear set up?
yes. i did mine on the 64 and 65 darts i had. lots of measuring, lots of trial fitting and trimming. i didn't have the luxury of a spare K with a double shear because, obviously, it was an early narrow body. basically follow what @Kern Dog posted up, but you just fab it up out of plate.