Proper Chain size?

1/2 inch chain is always a good choice.
as for the binders?? We use both lever for lighter tractors and ratcheting for heavy tractors. Ratcheting will get real tight

We use lever type and have been using 3/8" on ours. Some are 5000 lb. + With the loader we use a chain up front and in back and a strap on the bucket.

Its not the size, its the strength of the chain. I use ratchet binders, since thats all I have, on everything from my Cub to my Ms, so its a personal choice on the binders, which ever works best for you. Only thing I use a strap on is my lawnmower and golfcart.