hi50phd - I just use an aftermarket one (sending unit and gauge) from JC Whitney (124229 FUEL LEVEL GAUGE WITH FLOAT) on my main tank. there are posts here about it and it works awesome. very accurate I have found. if my aux tank has this hole ready for a sending unit, I will be adding one to this tank as well when I pull it off to clean it. Did not realize some have the sending unit hole and some do not, so I will not know until I take mine off to clean. I was hoping they were all the same and I could find out if they had one, I would order it and get it on its way. But now, seems I need to take it off to find out. ----- ducktapeguy - mine has very long bolts going through the tank as you describe. BUT, mine has 4 bolts, not 3. it mounts to the body floor, not the frame IIRC Ugly, dirty, but works. when I pull it to clean it, I will sand it all down and paint it as well.