Approx max rpm for this stepper motor?

I have a pair of Vexta PH299-01-A7 34 frame motors I want to use on this
lathe slide setup I'm putting together. When I got these, I was told
somewhere between 320-480 oz/in, can't remember. Dataplate only says
3V, 4A. Using Compumotor OEM 650 drivers at max current, anyone care to
hazard a guess how fast I might drive these, RPM-wise, assuming I can
generate the pulses fast enough?

I dug the other harmonic gear reducer out of storage, and it's 120:1
reduction. I'd like to have an ultra-fine resolution on the X axis, but
don't want to fall asleep watching it rapid. I know torque falls off
rapidly with rpm, but with that kind of reduction, I doubt I'm going to
lose enough torque at the screw to matter. Since I need to belt these to
the screws anyway, I might want to step the ratios back up a bit.
Thoughts?

Jon