Input Z of the grounded grid's cathode is Plate Z over mu+1. This is not typically a large value. For the 12B4, a plate Z of 1k5 at a reasonable OP is leaving a cathode Z of ~230R. It is a reasonable place to start.

A pentode's cathode Z is 1/gm, and with a high gm example( 36 mA/V ), a 30R value is the result. This gets near the 1:10 ratio output Z to load...

The pentode's g2 can be done with a simple dropping R and bypass C. Good quality C is likely to be worth paying for. A 1-2 uF and 30k should do quite well.

Using a triode as the CF/input stage also provides a means to adjust gain. Put a plate resistor in of equal value to the amplifier plate load, and gain gets cut by half( looks like a phase splitter, NO? ).

Cathode load can be a CCS, or resistor to ground( going to be small ) or to a negative rail. Going to ground will put a small resistor in parallel with the cathode load, and this will make the load appliedto the CF a whole lot bigger( maybe it will contribute to sound in a positive way? ). The negative rail will make that part of the load large in comparison to the cathode of the amplifier.

I am going to build *Something* new quite soon, just a matter of what....
cheers,
Douglas

I will see what I can do.
cheers.
Douglas