The 46 is only specified at its intended application, but like all tubes it does not "know" what the application is ... :^)
As a Class-A triode, it was operated (with G2 connected to the plate) at 22mA to act as a triode driver, transformer-coupled to a pair (with G1 connected to G2) in Class B push-pull. But the plate it rated to dissipate 10 watts, the same as a 45, and the Cunningham spec sheet shows the Class A plate+G2 curves up to 80mA. There is no obvious reason not to use it as if it were a 45, at ca. 35mA current. The mu is a little higher, and the plate resistance a hair lower, but using cathode bias as in the Stereomour I'd expect fairly similar operating conditions.
That said, I have not tried it - so don't blame me if you fry the tube or something else goes wrong!