i removed my fuel cap for the same rust reason, and welded it up n smoothed it etc

its a mare to locate the cap anywhere drastically different and still retain the existing fuel tank, as there isnt much of a direct route to the tank entrance other than the existing pipe route, due to the rear chassis rail etc. im buyin an alloy fuel cell now cos the pipe route to the normal tank would end up kind of messy

also, when smoothing the cap area, u wil find that the rear quarter is a slightly different shape to the other side, it isnt completely flat, it very slightly flares out towards the cap area, so wen it comes to filler, u wil always end up with high spots round the rim of where the cap was, so filler kinda needs to be spread far and wide to lose it lol