Sleve,
Why not just pull the tank and send it to a local radiator shop that has a dip tank large enough to accomodate it? The job will be thorough, chemically correct and they can even provide an interior sealer if you wish. Costs? Here in the Woodland, CA area it is about $60.00 and it comes back squeaky clean too.
Normbc9
I would love the name of that shop. The local guy here in West Sac wanted $100 to do mine. I'll drive to woodland to save $40.