Welcome!
220volt is better if you have the service for it. 120v will do the job.For the price you've quoted these are arc/stick welders- a little harder to use but will do the job.The best welder to get would be a mig welder ($$$$)
Can't believe someone put the belt directly to the axle! When you price a secondary or gearbox you'll understand why it didn't get one!!!
I'm currently building a 440 powered buggy if you want some info just go to this thread:
http://www.buggymasters.com/forum/showthread.php?t=2022
might be something in there for you.
Post some pics- that'll help all of us to see what you're talking about!!!