217 on 40 acres is rough, been there. Best thing I ever did was rent a mini excavator for a weekend instead of grinding every one, saved my back and my sanity. If you can burn them, wait til fall when it's wet out so you don't torch the whole lot. Also check if the county has any rules about stump burning first, got a fine once for doing it in August. That many stumps means somebody clear cut it years back and just left the mess, so at least you know what you're dealing with now.