Fuel tank rust

i realize it's not Mopar but I have another classic (1930) that is getting some rust starting in the fuel tank. Tank was exceptionally clean when restoration was complete. I was using 10% ethanol blend until a couple of years ago then switched to non ethanol premium. I live in a low humidity (on average) area and vehicle is stored in a very good building not getting below
40' F.
Does anyone have any ideas how to prevent the rust or at least to greatly reduce it ???
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