I have the same problem, it seems the wieght of gas station fuel filler hoses tend to roll the edge over and one tab on the cap pops loose. I purchased an exspensive used filler neck from Spector Off-Road and it had the same problem.
The fix I did was bend a near u shape on a cheap flat blade...
Looks like a nice vehicle at a resonalbe price. Is it a manual transmission or automatic I'm shopping for a 60/62 for a friend who likes to shift shift her own gears.
FYI, While checking craigslist in Portland Oregon area I noticed ther were some resonable priced FJ80's up there that may...
'75 was a transition year moving the marker lamp from the side cowl to the park/turn/marker light assemby. Your third wire is for the marker lamp to connect to the wire harness near the location of the cowl were the early marker was located. On my '77 the marker and parking lamp wires are...