exactly right. No need for food grade. I would look for one that had a petroleum product in it, they are usually unlined. Feed stores, fuel depot's, candle makers, there are lots of places you can find barrels for little or no money.
It makes no difference whatsoever what was in the drum as you will be taking it all down to bare metal anyway and burning it out at very high temperature. I strongly discourage you from a food grade drum. They are actually a huge pain in the butt to get the liner out of.
You will want to drill your intake holes before Burning out. I think two pallets is about right for a real good burn out. As soon as the barrel cools you can sand any remaining paint off and paint. You want to also wash and scrub the inside out and oil it with vegetable oil or cooking spray so it doesn't rust. It will rust pretty quick if you don't get it coated fast. Make sure you are getting open head drums with removable lids.
You will have to cut the tops off and use weber kettle lids or something similar. I would see if you can find them with removable lids if you can.
