Any data on the rated speed?
I've not played with treadmill motors myself, but most of the specs I've seen, show rated power at pretty high speeds. I was considering one rated 2 HP at 6000 RPM and another rated 1.5 HP at 3250 RPM, some time ago. Shaft torque seemed pretty low on both, with the lower-powered but slower motor looking much more useful.
In the end I went AC instead.