The problem with the space is such that I can not run the pulleys required
to use a 1750 RPM motor. The motor itself could be quite a bit bigger
than what I have. Of course, a 1750 RPM motor with a VFD woud get me
where I want to go, and allow a higher spindle RPM which I've been longing
for. I

You'd be EXTREMELY happy with the final result here. Variable speed is real
nice. Its got me plumb spoiled, can't have a lathe without this anymore.

Your costs go up as you increase motor size, but you should be aware that a
VFD/motor running at 1/2 speed has 1/2 the horsepower, etc. So, if you'll
use this at low speeds you need to oversize the motor and VFD. Of course you
could still change belts for low speed and not have this problem.

Karl