yeah there's a simple and safe way to do this. TAKE IT TO A RADIATOR SHOP, AND HAVE IT BOILED OUT AND TESTED! if you have a doubt, then there's a good reason for it. better to not mess around with gas, don'tcha think?
most radiator shops can coat the tank with this stuff that prevents corrosion from ever starting again. good investment. most of the time the tank comes back with all the paint gone, so it's a good time to prime and paint the thing, before the rust starts again.
