I know that once upon a time we traded for a 1969 643 cornhead (check serial number books). We rebuilt a 1243 cornhead and used extra parts to update this old cornhead. I would assume that if this cornhead was a 1969 model, that the 1969 model combines had the new style feeder house. As far as the time it took to switch heads, unless you had an older combine, it is hard to believe how nice it is today compared to then. In those days, the feederhouse was part of the head, and to switch crops you detached the feederhouse, probably changed sprokets for the cylinder as there were no variable speed cylinders, and maybe swithed screens. That is one reason farmers stayed with beans until they were finished before switching to corn. It was a half-day job.