[Dennis Craft]

I agree with Charlie, switch to the 6 volt filament equivalents and use the 6W6 in lieu of the 25L6. The 6W6 output impedance is very close to the 25L6 which would help to preserve audio quality. I've done this in the past, but switching from 2 volt filaments to 6 volt versions. It still preserves the authenticity of the set until a correct transformer can be found. Maybe place a note inside the set as to what you have done and why.
Regards, Dennis