I just bought a 1988 1640 Case IH. I'm looking at a bean head and am wondering what is the biggest size I could put on it. I've heard alot of people tell me to go with the 17.5ft 1020. I can't seem to find one in decent shape anywhere. i've found a bunch of 1020 20ft all over the place. Would my combine be able to handle that big of a head? I sure hope so, its looking very grim for a 17.5ft.