[Amps] 3CX400A Substitutes

[Jennings]

I have an Alpha 374A with a good pair of 3CX400As in it. They may last years but may also go west next week. One never knows. Has anyone come up with a suitable triode tube conversion or even a conversion to ceramic tetrode or tetrodes?. 

With a pair of 3CX400s worth megabux these days and becoming rare, I wonder if anyone has had the same problem or come up with a solution or have some ideas. 

73, Lee ZL2AL