If you don't need that large piece of Alu then you may be better off ordering form some one else other than mcmaster but mcmaster had the best price on that piece of aluminum. The belt I am using is from work and as I already stated the clutch was off of ebay. My belt tensioner I got from a lawn mower shop here in town. I think it was for a 3/4 inch belt it was about $10. Most of the bolts are stainless 1/4 20 annd 2 inches long.
Good luck, I can't wait to see what you come up with.