[Mondial]

Are you sure one end of the original primary went to the chassis? It doesn't make sense because there would then be no plate voltage on the 71A. How many leads were on the original transformer?

I would think that the primary winding would connect one end to the 71A plate and the other to B+, which is the 
+side of the filter cap. Then the secondary would connect to the speaker coil and ground, provided one side of the speaker coil was also grounded.

In any case, either the choke or the output transformer will work, but if the transformer is smaller it might be more convenient. Connect one end of the winding to the plate of the 71A, the other to the 
+ siide of the filter cap. Then connect one end of the .47 uF cap to the 71A plate, the other to the speaker. The other side of the speaker would connect to chassis or the - end of the filter cap. 

You want to make sure the cap is in series with the speaker, so it will block the DC voltage on the plate from passing through the speaker coil.