Thats awesome man. I just picked up a 1966 4x4 with factory a/c. the 4x4 trucks are a lot more rare and desirable. As fare as a fuel tank your options are pretty basic since the trucks only have one line from the tank to the fuel pump. You can do what most do and get a fuel cell or a custom tank made( more expensive). Putting it in a truck box would be pretty sweet and keep it protected as well. Are you going to be using it for heavy off road use or light? I don't know where you're located but i'm in Oregon and have some extra parts if you're looking for something let me know, might be able to help another k20.