I run a 920 on my 6620 T2 and I've never needed to move the fore-aft. Which means I never tried to figure out how to hook it up. As far as the reel speed, I run it "by the seat of my pants" by using the reel speed adjusting knob. It works fine for me, but then again,,, I don't know any better. lol
I do find though that as conditions change during the day, I sometimes need to run the reel slower or faster while ground speed stays the same. That makes me wonder just how useful the automatic feature may be over the long haul, but like I said,,, I don't know any better.
When i was a mechanic at the local JD dealer, we set up a 7720 for reel fore-aft. We had to install a splitter valve in the cab and tap into the auger swing circuit. So if you moved the splitter valve to the reel position, you just used the auger swing handle to adjust the reel fore-aft. This was a fairly simple thing to install. As for the reel speed, i'm not sure what you need, so i won't even venture a guess.
If you go to your dealer you should be able to get a parts list and a picture of the plumbing to run for/aft, then only trick is the special fitting you have to put in the valve to get power to the new valve you add. Auto reel speed would not be economical and to many parts to get to work, if I explained how it worked, just trust me on that, but the fore/aft is not that bad. I have done many of them. GL
Just a curious question, but are you sure that you really want to add these attachments/options on your combine? I understand that the newer 900 series head would likely have them on it and the 20 series combine would not, but we have run 930's on 9600's and a 9610 for many years and in the later years have abandoned the fore/aft altogether and even the auto reel speed we typically do not use. One potential problem you will have with fore/aft is a cylinder might start to leak internally and you will have to be pulling it back continously during the day (as well as added wear on the reel because likely only one cylinder will leak and the reel twists). There is also the possibility of accidentially sliding it ahead while you are combining; the reel goes directly into the ground when that happens. The reel on our head with fore/aft cylinders is now bolted so it cannot move anymore. For me, it isn't a big deal to change the reel speed manually even after using the dial-a-speed. Also, the delay time can take too long to change to the desired reel speed anyway. For example, if you are like me, you speed up a bit when you turn around on the ends. When you slow down to begin combining again the reel is turning too fast and the first bit of beans you cut get hammered hard by the reel. Running it on manual eliminates that issue. For you these options might be just the thing, but for us, we simply found that they weren't all that useful. Just a couple of thoughts.