I can’t say for sure with a tube amp. The other amps techs on the forum may have some input on that.
A simple way to do that, though, would be to use two simple switches. Wire the input connector to both switches, like a Y-split. Then wire each switch to an output connector.
When you switch, switch one cabinet on before switching the other off. Of course, you don’t want to leave it connected to both cabinets simultaneously for long, especially while playing, because the total impedance seen by the head would be lower than its rating. But, a quick second or two while switching over shouldn’t be a problem.
Of course, this is only a consideration if you want to do a “make before break” system.