I am doing work on a J3 which has a 6 gallon wing tank installed in the left wing. There is nothing in the aircraft records which states when the tank was installed or where it came from. I know there is a tank listed in the TCDS, but I have no idea if this tank conforms to the drawings it mentions. I would like to identify this tank and get a proper 337 done for it. Can anyone tell me where I should start?