2003 CHEVROLET EXPRESS 3500 Fuelpropulsion System Problems

WHEN THE VEHICLE FUEL TANK IS FILLED, GAS FUMES ARE DETECTED AND SOME FUEL CAN BE SEEN ON THE BOTTOM OF THE TANK (A FEW DROPS OF FUEL). AS THE TANK CONTENTS LOWER THE SMELL AND LEAK GOES AWAY. AN ACCESS HOLE ON THE SIDE OF THE VAN REVEALS THAT THE TANK HAS A SMALL LEAK WHERE THE PLASTIC FILL NECK WAS BONDED TO THE TANK. THE STEEL FILL NECK AND RUBBER CONNECTION LOOK FINE. THIS IS A CONVERSION VAN W/O A LEFT HAND DOOR. THIS VEHICLE WAS BOUGHT FROM A SOUTHERN CLIMATE AREA AND IS ONLY RECENTLY BEEN BROUGHT TO A NORTHERN CLIMATE SO CORROSION IS NOT SUSPECTED. SINCE I SEE NO RECALL OR MANY COMPLAINTS, I AM LOOKING TO REPAIR OR REPLACE THE TANK. CURRENTLY LOOKING FOR A SEAL MATERIAL THAT COULD BE APPLIED TO THE LEAK AND THAT WORKS ON POLYURETHANE AND RESISTS FUEL. HAVE NOT FOUND...