I have lost the gas cap to my 50's pressurized gas can. There are currently 2 on eBay, but the seller can't give me any information about them other than he claims they are OMC/Johnson/Evinrude. Are these likely to fit my gas can? The pictures look close to what I expect, but I would hate to spend the money on a cap that doesn't fit when I could have put that money towards a fuel pump and new can.