Chems:
If its quoting 1.75hp then thats about 1.3kW. So I'd be looking for a 1.3kW motor that I can hook up to a speed controller. Hmmmmm
For the belt drive?! No way it's that strong. It would be closer to 1/4HP (~200W).
I would suggest looking for a large worm drive (right angle) motor. A larger windshield wiper motor would probably work. Something to look at would be the diameter of the motor's output shaft as it is a good indicator to the motor's strength; you should be looking for something with about a 1/2" (13mm) shaft.