Re: old gas tank restore
Cleaning would depend on what's in it. If it's just gas residue, rinse with a strong solvent of your choice. It it's rust, you'll need to electrocute it.
There are only a few parts that normally need replacing. If it's a dual-line pressure tank you may need to replace the manifold gasket if the tank leaks or won't hold pressure. If the primer button on top of the tank fails to prime, you'll need to replace the diaphragm. Both these items are under $5 each. Then there's the o-rings in the end of the connector. They're only a buck and a half each but sometimes a pain to replace.
As far as paint, I'd paint it red. Available from Wal-Mart. Or if you really want to be authentic you can order a spray can from
www.nymarine.ca. After shipping, packing, handling, Foreign Transfer Fee it'll run you about $40.