Still running mine at 5100 hrs. This fall went up against a 9500, 9600 and a 9650. The old girl out paced and out cleaned the newer machines. Had my younger brother running it while I was running the neighbours 9650 as he was in hospital through harvest.
The segmented enclosed Sunnybrook with 8 bars around the circumference works well in harder to thresh crops. The 4 bars around the circumference are ok in easy threshing crops but fail in hard to thresh crops.
The air foil chaffer makes these machines much easier to set and keep a nice clean sample through out the day. Also gives them a boost in cleaning capacity. I am looking for a lower sieve currently as mine has wore to the point of needing replaced.
Walker risers,.....3 per walker is lots. I'm pretty sure that is the most you can put in them.
Still running the stock beater drive.
Concave, well, I got mad and built my own. The best way to gain capacity is to have the machine separate as much as possible at the concave instead of relying on the walkers. To separate well you have to remove the filler plates that everyone wants to put in the front 1/3 of the concave. Mine has more bars up front to hold the crop mat up in the rotating cylinder and leaves room for seeds to fall through, spacing gradually gets wider between bars as you progress toward the back of the concave. Wire spacing is 2 inches
As for capacity. You can keep her at this level in wheat all day long. Just keep an ear open for the main drive belt under the seat starting to slip.
Treat the old girl well and she will pay back many times over.