Hi Chazz, I have an X3 ( Grizzly Go463), one of the first mods was the belt drive, I made the parts to the specs in an article posted on a Yahoo group and this was the result,

Uploaded with
ImageShack.usI rechecked all the numbers, belt, pulleys and original gears, all the numbers matched. So I'm guessing the center line distance on my mill is different from that of the author. As you can see the first pulleys were from scrap anyway, my first foray into timing belts.
I used this calculator to figure out the number of grooves/teeth for the belt I had - 9mm - 5mm x 300 HTD
http://www.sdp-si.com/cd/default.htmAnd this is the end result, as you can see this is a fixed distance so I lucked out. I ended up with a 34 and 36 tooth pulley

Uploaded with
ImageShack.usThe hard part for me was figuring out the actual radius to drill at, as it turned out I was off, too big but I was using an 1/8" drill so I just used an 1/8" end mill to clean it up, oh and the other hard part was getting the right pitch using what I have, a spin index, it doesn't do 34 but the original drive gear was 34 so I index that and used a scribe in the collet.