(He doesn't want to spend the money to go to the hub motor.)
What are the chances of unbolting that transmission and bolting it to the new motor? Probably requires some ingenuity on your part.
http://endless-sphere.com/forums/viewtopic.php?f=6&t=3249&start=30
Wonderful post with things to say about the eZip motors.
http://endless-sphere.com/forums/viewtopic.php?f=6&t=1273&p=19346&hilit=Kolmorgen#p19346
I'm just getting more confused. Doesn't help that the Currie site doesn't list replacement motors. (So no factory spec on RPM.) Do you have a 20t freewheel on the wheel? Just stuck guessing at how your bike works. From what I'm reading your output on the motor should be between 400-450rpm, but no guarantee that's right.
http://www.conhismotor.com/ProductShow.asp?id=290
If you want to use that motor, you want to do a reduction to perhaps 387rpm at the wheel to go 30mph. It comes with an 11t pinion. With a 20t sprocket you can go 125mph, once it struggles up to it. (Well, probably never, actually.) More likely the overloaded motor would burn up first, especially going uphill. I assume you cannot get this sprocket onto your wheel, but it would be the right size. https://www.curriestore.com/bikes-scooters/SD-350201317208/ Just the sort of experiment I'm supposed to be making time for. Perhaps someone has a solution already.