Good work Andre. George Blake actually lives less than an hour from me, and we have met a few times. All of those differences listed are correct. Here are some of the things which do interchange, which may also be of some help. I also have a couple of extra 920 parts saws, and I used some of those parts on my 910. The key word here is "interchange", ie the parts may not be exactly the same, but they will work. Sometimes with slight mods. For instance, the top covers on the 910 and 920 are the same with the exception that the 910 cover has the hole for the top mounted deco.
The clutch side covers look to be the same, but I haven't actually moved them back and forth to confirm it. Even though the 910 handle goes on the inside, and the Partner style handle goes on the outside, they look the same. (I just went downstairs and looked)
Starter covers have some interchangability. The metal covers on the 910 are the same as the metal covers on the early 920's. But something else changed with either the flywheel or the starter pulley when they went to the plastic covers, because I was unable to use a metal cover on my newer 920. But, it could probably be made to work. I didn't need to pursue it, so I'm not sure what the deal is.
Intake and exhaust stuff seems to all be interchangable. Mufflers, carbs, intake boot, gaskets and such. These are some of the parts that I would guess would be more popular when getting a saw to go from the project list to the running saw duty roster.
My experience here is just 910/920, so I don't know how much of this might apply to a 930. Some things I haven't looked into yet are flywheel and clutch differences. Yes the 910 has a different clutch than the 920, but can they be swapped? Beats me!
Either way, anytime you have an opportunity to get a 900 series parts saw, I'd say grab it even if it's not the same model. There is enough stuff that you will be able to use to make it worth while. The same probably applies to the 820/830. After all, parts for these saws are just going to get harder and harder to find.