So of course each furnace line has a different (in my case) #Rheem#part#number for the motor, even though all of them are actually the same 1/2 HP GE motor and controller -- they've just had different #settings "blown" into them.
And if you try to use the "wrong" motor from another furnace, the control board says "no way!" and won't work.
So Rheem gets to keep #selling#parts that are #exclusive only to them, and only for one model of furnace, so they're stupidly #expensive.