I purchased a repop filler neck for later model a body. For my 71 Demon. I compared the length and trimmed to length of original at the tank end. I installed from the backside of the qtr like original and drilled three new holes thru the mount flange of the tube. I can buy gas caps thru rock auto for 4-5$. Another benefit is that it has the flapper which helps with the blow back while filling. I did have to tack weld the splitter in the tube on the tank end after cutting. I then coated the welds with fuel tank sealer. I don’t think they even used that ecs cap for a full year. Best picture I’ve got. 1973-1975 Dodge Dart Parts | MF46201 | 1973-75 Duster & Dart Sport - Fuel Filler Neck | Classic Industries