I would definately get the A series header. We have an 853A and use it harvest down milo. the second year we had the header we put lovejoy belt and chain tighteners on it, what a time saver!! it cut our daily maintenance down considerably and seems to make the belts and chains last alot longer. I really think it was money well spent. We just did a major rebuild on ours (new gathering belts, sprockets, knives, welded a new floor in it, and a few other minor things) we bought alot of the parts from sloan express, definately the cheapest place to get parts. Good luck!!