Further thoughts: According to this web page on rectifiers, I think I have a full wave rectifier so I need to divide 350V/.45 to find the transformer voltage rating, which is about 770V.
Rectifier web page:
I found this transformer that might work:http://el34world.com/Transformers/files/MOJO756.pdf
More info here: Fender Transformer hookups
The MOJO756 has two 384V windings, which adds up to 768V. The page also specifically says that it can be used with two 6V6 output tubes, and it has a 6.3V winding that can supply up to 3A.
Can anyone that has a bit more experience than myself comment as to whether or not this transformer seems electrically suitable?
The transformer has the wires coming out the bottom, which is also suitable for my amplifier.