I need to know if there is a way to get the gas cap completely off the tank!! Even the guts that remain once your cap is off.. Does this unscrew completely off the tank or is it spot welded and a permanent fixture. If so, is it possible to remove the fuel pump and get your hand up inside to the roof of the tank to screw a lock nut onto a through wall fitting? BASICALLY I AM WANTING ACCESS WHERE I CAN GET MY HAND INSIDE THE TANK..