$50 tops if pump doesn't work $80 if it does. One less thing to have to repair if good.
Don't worry about the base shape so much especially at this value range. You can get picky later if you want, but as a first acquisition I say go for it!
Spend $3 and pressure wash it at the self serve car wash and see what the real condition is. If not rusted through, you could simply have someone sandblast it and you can then paint it yourself and save $$.
I would guess a local auto body paint shop would charge $300.
Most guys tackle these since it's mainly a strip repaint job. Nothing fancy. Also, that's why I say pay a little more if the pump does work, means you don't have to disassemble it, just flush the tank with degreasing agents.
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Collecting anything keeps you young at heart!