They only showed up in late production, and many were removed during service and not replaced. Fuel line brackets were 'STAMP RITE' and the power brake booster vacuum hose bracket 'AAc' (same as the F&R licence plate brackets).

Not to get off the subject and highjack this thread, but the 69 license plate bracket also used another stamp, which I feel is more correct than the ACC. This other stamping is a "C" and I have included a picture. I also have two NOS with no stamping at all.

If you want to start another thread about same for further discussion please do so, for I'm sure there are others interested....Thanxs Dave

Bracket is the same one used on LT1 Corvettes. I've never seen one painted black.

June build car
 

Aac stamped

Sam just shipped me a set of original studs last week. I'll measure them and have a look to see if the bottoms are dimpled like other examples in this thread. Thanks for the pictures and lengths folks.

Dave, didn't mean to suggest only 'AAc' is correct, just that it is the same manufacturer and stamp as used on those parts. As with most components, GM probably had multiple suppliers to avoid shortages.