Fiat 850 gas tanks and engine conversions

[Abarth750 <Abarth750@domain.elided>]

I recently pulled the tank out of one of my 850's to be cleaned and sealed.
The problem is twofold. around the fillerneck there are two gaskets. One goes
on top and this is the one you see on top of the car. the other is a foam
material between the top of tank and body of car.  This second gasket has
caused some rust as it has trapped water.