determine which idler arm I have
From 68/ later there are only two unless it was something weird like BB/ hemi, I know nothing of those
Up through 72 the "studs" pointed up, 73/ later they pointed down
"Old style" up through 72 studs point UP
73 / later studs point down
There are FOUR parts concerned with this swap regardless of actual year of car:
Pitman arm, steering box (large/ small spline), idler arm, and the center link