I do remember one which unscrewed, but not which car. Probably the '58 pontiac, weren't that many of them around anyway. Vettes were the worst, with the cap in the middle of the trunk and all that freshly polished fiberglass to drip onto....
Ok, I think your memory is better. What was the one that had the gas tank opening behind the back license plate that had to be flipped down?
Thanks in advance. (Was it an Olds?)