aren't all the panel tanks the same regardless of model?
The 1/2 and 1 tons used different tanks. The 1 ton had a larger 18 gallon tank. Not that this fact really makes a difference, except that new 1/2 ton tanks are available, while the larger 1 ton tank is not.
I think with what has been done to your tank already, there is little you can do at this point easily fix the tank. Yakimabowties solution might be your best bet.
One sure fix, perhaps the best long term, would be to buy a new 1/2 ton tank, which would be just like the one you have.... and deals done.
off the topic: I once lived in Mukilteo, just off the Speedway.
