Shryp: The double speed may not be a show stopper. You could set the friction disk to be as close as possible to the center of the drive plate and that would be 1. You could crawl along at the expense of chewing off the friction disk but even at an increased rate would take many years before it had an effect. 2 would be faster than normal 1 but with the 6.5 GX200 you’d have enough power to clear at a faster rate. Your machine is only 22 inches not much to load into the impeller. For massive storms and nasty EOD you could just take a smaller cut. For the rest of the driveway with freshly fallen snow 2 would be slightly faster than a normal 1 and not much of an issue
Also, to offset the speed increase you could go with a pulley change.
PeteF: I think you mean the crank case cover. Are you sure you have all the bolts out?
You can try a rubber hammer with lots of light blows on the side going from back to front.
Sometimes industrial razor blades work. Those are like the old shaving blades but not so great for shaving. Wedge it in and lightly tap it in further. Do that at a number of places over and over.
I have blades I got a flea market that were for some industrial application. They are super sharp and very thin. If the razor blades do not work I use those. Worse case you could use a thin knife but only go in a short distance in many places over and over. Eventually all the slight movements add up and the case break free.
One of those motors bus708 listed might. I only got google hits on one. It seems to be in the same family as yours so may work.