[MrFixr55]

Hi Jordan,

The following Primary Impedances at a 250V plate supply for Class A Single End output (as opposed to Push-Pull) from the RCA Receiving Tube Manual RC13 (1937) may be helpful:
For 41 or 6K6 7,600 Ohm
For 42, 6F6 or 2A5 7,000 Ohm
For 6V6 5,000 Ohm (from RCA manual ver R24)
For 45 3,900 Ohm
For 47 7,000 Ohm

I would have to leave it to the Philco PhDs, but I am surprised that a 1936 or 1937 radio has a speaker with a voice coil impedance of only 1 Ohm. I am also kind of surprised that the same transformer is specified for a 45 or 47 tube as their load resistances are so different, unless the speaker used for a 47 had a somewhat higher impedance than the speaker used for the 45.

Voice coil (and transformer) resistance and impedance are 2 different things. Impedance is usually measured at a specific frequency, as it may differ for different frequencies.