Now, many years later, I'm dealing with 220V single phase power at the
house.
Does it make any difference which conductor goes to which blade on a 220V
plug? Obviously the ground goes to the round prong but there are the two
remaining blades: one oriented vertically; the other hortizontally.

No, 3 phase has to hit the motor in the right sequence. 240v is symetrical,
so the sequence is the same either way.