gas tank dilemma..........

Just drive it, problem solved!

The problem with welding a drain bung into a new replacement tank is that they're galvanized. Welding the drain in will burn the zinc off the inside of the tank at the weld and then the unprotected metal will rust. It would only be a small bit around the weld, but it would rust. So you'd either have to re-galvanize the tank or do some lame coating on the inside. Still an option, but not quite as easy as just welding in a drain. And needless to say never weld on anything that's held fuel unless it's been cleaned and properly treated.