Working on an aluminium fuel tank. Replacing a fuel level gauge. due to gasoline smell when full. Definitely leaking there, small hole on top of sending unit. Cleaned up the area where the sender sits with a bristle brush, quite a few pits in the tank around where the sender sits, no holes and it looks like electrolysis pitting. Nowhere near through the aluminium, so I want to fill it level in situ before installing the new gauge. Any ideas on the best filler would be appreciated, but no welding please.