I have good ones for supply and return lines just under drivers side and another one just before input to the carb. As Razorwire said, use good stuff.
As far as your tank and fuel cell issues, I also used Nick (Mickmate) to convert my 42 gal after I ripped out the rotting cell. He did a nice job for me. One tip that I wish I had asked him for was a drain plug in bottom of tank.
