If you tried, the 8 ohm cabinet would suck up twice the power of the 16 ohm cabinet. Exactly what the effects would be depend on the frequency-dependent impedance and the sensitivity of the drivers.
You could try it, of course, but don't expect too much.
Now, if you want to trade your 8 ohm vintage 412 for my 16 ohm vintage 412, maybe we'd both be better off...
Isaac