Texas was very helpful when I needed to prove that they titled my truck by the engine number instead of by the body number. Here in Washington I had to have the truck inspected to get the title changed. They wanted to assign a new number, but I asked that they use the body number instead.
As for the crack, I'd start by trying the least intrusive fix, and working toward the more drastic. I don't think you have a pressurized cooling system in the first place, so stop leak may take care of the problem. I'd save drastic action like welding for after the other approaches failed.
Just my two cents...
