Hi metalmeltr, You're in pretty good company here, as a couple of the members are also metal workers. I don't know of alot of sources for motors, but I do know that people who experiment with electric vehicles make use of used electric forklift motors. You might find some sources on the web for these. I'vr ran across them from time to time, but I don't have the links. Anyway, good luck!

PS: Also, look up e-tek motors. They are small, light and powerful. They are also expensive, but you can sometimes find used ones on e-bay.

Just get the parts for a standard issue golf cart drive system. Its going to be nearly a plug and play system with that.

As for finding larger DC motors, surpluscenter.com, eBay, and any industrial parts supplier will carry an overwhelming number of motors to choose from!

A basic modified golf cart drive system and surplus motor should be under $300!

I will be finishing up a electric conversion of a Polaris ATV this fall and the motor and controller for the electric drive system cost me about $250 total!

What type of battery's and charging system you use are what will make it a cheap of expensive project.

Just a thought.
Use a transaxle out of an old riding lawn mower if you find a high speed motor. Take it apart and clean out the thick grease they use and replace it with a 50/50 mix of synthetic grease and gear oil. It will then have the proper lube for running at around 10K RPM inputs! (about 30 - 40 MPH in high gear!)