Gas cap Lock?

Yeah the '71 caps are kind of a pain in the butt, both my GT's have that one year only CA model cap.

I bought one of those flip cap adaptors for one of my cars, and I pulled the filler neck out of my '74 parts car to replace the other. They make locking caps that are readily available for the later style, might be worth switching. I like to have a locking cap regardless, just cuts down on the possibility of vandalism. Plus I leave my keys attached to the cap while I fuel, that way I can't forget the darn thing.