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.
Possible, but silly. You need a much higher perveance tube to get even mediocre efficiency and distortion performance. That's why people use 6080s, sweep tubes, and the like.