Well - bad news to report...
Once I received the motor and applied 12V to it, I realized that the 88RPM output was going to be too slow. I was thinking maybe I could use a cogged belt and pulleys to step it back up 2x or 3x in speed (with a matching drop in torque). I machined an adapter to replace the plastic splined 'gear' on the motor with something I could attach a pulley to:
Then tried my first attempt at broaching (on my lathe) to create a keyway in a shaft collar to replace the crank handle. As a first test I made a simple adapter to connect those two together so I could estimate whether the motor would have enough torque to handle a 2x or 3x reduction and still drive the shaft:
Then I gave it a try:
Unfortunately, the window lift motor doesn't have enough power to drive the shaft at all (either up or down). This was being driven from a 12Amp 12V bench supply, so I'm pretty sure that lack of input power wasn't the issue. This was disappointing, because with the built in worm gear it seemed like this motor should have been strong enough to do what I needed. Of course, without any specs it was all just guessing anyway...
For my next attempt I had read some folks suggesting the motors from cordless drills. I just happened to buy two at a hamfest last weekend for $3, so I gave one of those a try...
Similar results - not enough power from motor to lift the head. The drill motor did have enough power to lower it though.
So, anyway, it seems it's back to drawing board. I know that "Hoss" (g0704.com) was able to drive the stock z-axis lead screw from the top (vice through the crank handle gear) with a 570 oz/in stepper motor, but going with stepper motors and controllers is a bit more than I'm willing to do for this upgrade. It's not like cranking the handle is all that hard - I just thought it sounded like it would be a fun, cheap, simple mod... oh well...
I'll probably try the window motor on the x-axis shaft, just to see whether it has enough power to drive that -- that'll be academic though, because I already have a Grizzly power drive for that axis. But maybe that info will help someone else out in the future...