I think they are 1/2 supply & 3/8" return.
You will have to do some work to make the dual tanks functional. Check out the fuel tank switches used in marine applications. They are made for high flow & also switch the return line as well.
You will have to do some work to make the dual tanks functional. Check out the fuel tank switches used in marine applications. They are made for high flow & also switch the return line as well.