How do I reinstall the trunk latch cover on my '64 cuda?

You post here asking for help, and then berate us when we point out that accidental swapping of a hood latch with a trunk latch is not uncommon. Not cool, and I don't think it is helpful in solving your problem and will probably turn a few people off to assisting you should you need additional help in the future. If these are indeed the original parts, and the correct ones for their location, they should fit if you play with them long enough. I'm out of new ideas at this point. Good Luck!