Looks like it was an original Belvedere. They couldn't find a gas cap and didn't bother to smooth it. I guess it's the plug-in.
I have never cared for the full rear fender cut out look on those cars. I remember a friend having a 1967 GTX that had rusty rear quarters (Ontario Rust Belt car). This was 40+ years ago, and he bought a pair of junkyard front fenders, and grafted the wheel well area into the rear quarters to repair the rust damage. I did not like the look then, and still don't.
Hey RC, not so hard on the 66-67 body style. They don't need to be butchered either.Well, at least they didn't ruin a Charger or Road Runner. Yet.
Especially when the stock front wheel well openings are not perfectly round. They at least could have made the rears match...The problem with the butchered quarter is it looks like they took a string from the hub center and made a perfect circle around the wheel. NOBODY does that except gm and furd.