[Phlogiston]

https://www.tubesandmore.com/products/tr...tage-10-ma

I'd give this a try. Line transformer is designed a relatively low impedance line to an even lower impedance voice coil.
At 10ma it's pretty close to the max plate of the 6R7. The ratio maybe a little high at 1:3, may need to load the sec w/a resistor across it. Price is good.

GL

These are good. I've used at least 100 of them. They are a great replacement for 1920s and 30s radios where volume was more important than fidelity. Good price too.

But this is an interstage trans, not output - as in the thread title.