I'm pretty sure that almost all standard grinders use AC motors. Just make sure it is a Totally Enclosed Fan Cooled (TEFC) motor to keep the steel dust out of the inner parts and to keep it cool. Pulleys work great, of couse not as nice as a variable speed , but you can always upgrade later on. Someone who knows more than me will chime in on this as well. Good luck man.
I just finished build an NWG (No Weld Grinder) with the plans from usaknifemaker and It would have cost less than $500 if I did't waste money ordering the frame steel online, shipping is horrible and prices are way more than a local steel/scap yard that I found out about after I ordered it. I also got my motor for free which helped a lot with the price.
I used longboard wheels (kinda like skateboard wheels but a lil bigger) for the tracking and idlers that work perfect and are great for using as contact wheels as well on the flat platen, or you can even make an extra tool arm using the 4th wheel that comes with the set. I got a set of 4 of them that came with bearings for about $40 on "that auction site" and these bearings accept 5/16 bolts (they're just normal skateboard wheel bearings which are very tough) In case you wanna look into these, the wheels I got are called "Abec 11 Grippins" which are ecatly 2" wide and about 3" in diameter. I got the idea from another maker that made a belt grinder using these. Here is a link to a short vid I made of mine that I finished a couple months ago.
https://www.youtube.com/watch?v=aNMuKGMcqlc&feature=c4-overview&list=UU2rJM5fwM7F-Fy9E74-fYSQ Hope this helps some
-Paul
www.youtube.com/Lsubslimed