Congrats, Seth; I'm sure you'll be very happy with one of Troy's creations.
That shaped bumper grommet came in 2 lengths. And yes, those are early (to '67) grommets. '68- '73(?) grommets are longer (and slightly wider?) for the more substantial bracket and slightly bigger bumper, and '74 and on used the tubular telescoping brackets and (iIrc) used a triangular shaped grommet. Al