These parts have been custom designed to fit OEM door bullet mirrors for the 2nd generation Pontiac Firebird. I don't know if they will fit the reproduction mirrors for these cars. They fit between the door skin and the base of the mirror and provide a much better fit then the reproduction gaskets currently available.
Since these are meant for use in the weather, you'll want to print in ABS, not PLA. Also print with a minimum layer height to minimize the layer stepping on the top surface. Any stepping that occurs can be eliminated by light sanding on the top outside ridge.
The part with the large center hole is for use on the driver side to accomodate the remote cable. The passenger side, which doesn't use a remote, does not have the large center hole.