If we presume that the 300B needs 70V peak of drive, then using the 1626 to drive it would mean that you will need around 15V peak at the input of the 1626, which is about 10V RMS. You could definitely use the 1626 to do this, but it would need to be in a three stage amplifier. You could probably use two 1626s per 300B with some success.