Dwight,
As far as the tank treatment goes, if it were mine, I'd start with the Vinegar treatment for a week, then inspect and if necessary follow up with the Klean and Strip "Prep & Etch" for an hour or 3. That should have the tank looking good.
Definitely pull the petcock and gas cap and use rubber stoppers to plug the holes.
Quite a nice find and I know she'll turn out nice!
Charlie