[Eric]

Yes, the drawing is very helpful. Now it makes sense. The transformer is the interstage between the 226 fiirst audio and the 71A output stage. The common connection between the speaker and the interstage transformer primary is the B+ power supply, fed from the filter cap and 280 rectifier.

There is no output transformer. The speaker is driven directly by the plate of the 71A. 

This would be a better choice for the interstage transformer, as it has a higher turns ratio (and is less expensive!)

https://www.tubesandmore.com/products/P-T156

After some more poking around I think  the P-T124 might be a better choice because the one side that was not open I measured and I got 8.6k ohms which I call the primary  it was the connection to the 71A pin3 and the chassis and the primary on the 124 is 7k and it is rated 5w  
https://www.tubesandmore.com/products/tr...Interstage
 Thanks Eric