Output transformer impedance isn't critical. I would try to find one with an impedance around 10,000 ohms but anything will work. Secondary to match your modern speaker. An 01A isn't designed to drive a speaker but was the only tube available in the 1920's until 112A and 171A came along.
Norm
:How do I describe a properly matched output transformer to use with an 01A final output tube in an old T R F radio. I want to use a modern speaker.
:Thanks:
:Dorian.