Thanks for the responses y'all (and forgive my impatience )
I think you're right, hired hand, I thought there might be a way to invert the chassis (so the tubes hand upside down, like a peavey classic 30), but now I see that all those kind of amps have top mounted controls. My valvestate has the controls mounted on the front (same direction as the speaker faces) and there's definitely not enough clearance for the transformers and tubes.
I think I'm just going to build this up as a head and buy a 2x12 cab to go with it. There are plenty of good used cabs floating around Austin.
Thanks again - any suggestions for what I should do with the combo?