If you look closely at the pictures, you will see they added a return system on the end of the straw walkers. I don't know what other differences there were. In my area, there was only one 865 because MF was pretty much gone by that time.
Seems to me they may have had a small beater at the end of the walkers to separate out remaining barley kernels etc. You can probably see the small return elevator on the left side of the rear cowling which would pick up the tailings after they slid down to the inner return collecting auger. I think they may have been used in Europe for a longer time due to the humid conditions and very heavy straw load they run through their combines. The only one I saw was in Saskatchewan about the time Massey went out.
The 860's if pushed too much would start to throw over, especially as they are famous for "white caps" in wheat. Massey added the return setup behind the shoe to catch any "throws" and ran it back over the rethresher. I have heard it would pick up 1-2 additional bushels with this setup. Unfortunately the Massey division was being used as a cash cow for the Owner corp and they were not interested in the customers..funny about that!!