Gas caps?

The gas cap that’s currently on my 76 dart seems like it doesn’t quite fit right, it’ll spin endlessly with a snug spot at about a 45 degree angle to the trim line below, the cap is one of those chrome with black plastic block handle. I’m just wondering if this is normal, and if it’s not I’d like to replace it, ideally with a locking cap. Any input would be greatly appreciated. There’s a picture of what I believe is the cap I have now, or a close variation. 13AD0D37-5F7C-4020-B0D7-E0D93DD7926D.png