Every mopar I (or our family) had came originaly came with two keys per set. The round head is for trunk and glovebox (if keyed) and the pentastar is ignition and door locks. Pentastar first appears around 1968 IIRC, definately by '72.

Whether an aftermarket will wear or fail quicker than your old one is tough one to answer! So much of the new stuff is not so good to start with, so it depends on whether its a good quality repop as well as how much wear is in the originals. ??????

My own observation has been that keys wear quicker than the mechanism. And of the mechanisms, the ignition seem to get sloppy before the doors or trunks.

Not much to the lock cylinders. Might want to pull one and look at it. The pin cuts might even be marked on it.