[Chas]

Bryan,

This web site explains how to find the correct impedance transformer for your radio.

http://www.radioremembered.org/outimp.htm

The wattage would be the plate current vs plate voltage. Approximations can be taken from schematic values and characteristics for 6F6. Knowing how to do this is a learning curve, but well worth the effort.

Hammond manufactures quality output transformers but remember to look at the mounts and do not go over in wattage as they do get expensive.

Further, be aware that the schematic indicates the speaker has a hum buck coil, do not separate the connection of that coil to the voice coil. Do not exchange the field coil wires. You "may" have to swap the series combination of the hum buck and the voice coil if there is residual hum. That is the only place to make that exchange.

You "may" have to use a universal output transformer if there is no "close" match, such a transformer has taps and the correct one is used to match.

GL

Chas