Gotta be careful, Gasoline Reistant is not exactly gasoline proof. I've had luck with this one Seal-All Contact Adhesive and Sealant 380112: Search no more for the best Threadlockers at Advance Auto Parts
Just out of curiosity I checked out a replacement sending unit.. TELEFLEX Universal Electric Fuel Gauge & Sending Unit Kit | West Marine
a bit more work, but probably more piece of mind.