Hi all, I've got a small problem with my gas cap that I'm hoping to crowd source an answer for. I remember back in the 80's my dad removed the stock gas cap on the Duster and put on a locking gas cap, for obvious reasons as we didn't have a garage. Now I'm old enough to have my own garage and would like to put a regular twist-style gas cap back on for aesthetics. I've now tried a version of the stock cap I found in a scrap yard on another Duster, a version from Year One, and yet another version from Summit Racing, and I've got the same problem with all three: the cap will get just tight enough to sit in place, but it doesn't tighten to "lock". It just rolls through where it should lock and back to "loose". Is there a piece that had to be removed from the fill tube in order to make the locking gas cap work, and if so what was that called? What am I missing?