WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
I used a whole bunch of 1673 and 1638 in series for the anode load on a SE parafeed output stage proto once; I needed the inductance and I had them laying around. Very good sound. If 40H is enough for your application, I don't see what it won't work.