Of course there's a way. There's always a way, though it isn't always a good way!
Here's a way: instrument into Model T, Model T speaker out into Marshall speaker. Preamp out from T into power amp in on Beta, Beta speaker out to Ampeg speaker. The downside here is that you don't have the use of the Beta preamp. Or you could reverse the inputs, going into the Beta, Beta preamp out to T power amp in, speaker connections the same. Now you have the Beta preamp, but not the Model T. OTOH, you don't need an ABY box.