i dont knwo about the gas cap. it should work but those damn french and their over engineered hyper specialized parts. i have a '79 50v and my buddy has a '78 50v and a lot of the parts are specific to one year. whats more they like to use "french metric". that means if you ever need to match up any threading on your bike good luck. i took a screw into a hardware store that has an unbelievable nuts and bolts section and they couldnt find anything that matched the pitch of the threads. the guy was really confused as to what i had.