I would like to install an Aston fuel filler cap to my Triumph TR2, like the original race cars had. https://www.silverstoneauctions.com/events/2019-auctions/nec-classic-motor-show-sale-2019/nec-classic-motor-show-sale-saturday-9th-sunday-10th-november-2019/cars/pkv-374-the-ex-works-1955-le-mans-24-hours-triumph-tr2 I ordered a MOCAL aston cap with roller catch and 2,75" thread, however, it appears too small (Outside diameter is even slightly smaller than the original cap). Is the