Don't use a known cruddy tank. Get a new tank for something like an outboard boat motor or even just a plastic gas can, and plumb the fuel system to it. Old gasoline residue and varnish will be dissolved by the fresh gas and it will go straight to the valve guides. The SECOND time you start the engine, you'll have a bunch of stuck valves and/or bent pushrods. Enough crud will get deposited in the valve guides during the first run to trash the engine on the next attempt at starting after the engine has a chance to cool down. It's happened many times to several stovebolters.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!