maybe you need to go one piece ferther, the first casting after the sprocket you can not take off before you take the second casting of , because the shaft with the sprocket on is hold with a bearing and a locking nut on the second one.
I had the same problem with my d2. One side came apart with very little trouble. The other one has so much rust built up on the teeth of the clutches that I had to put pry bars between the housings and keep rocking back and forth. It took a while but it finally came off. I don,t know what else you could do because nothing is accessable until you get the housing off.
It is a common problem on a D2 for the steering clutch to freeze in the drum, it is somewhat common to break the drum trying to pull the final housing. all you can do is rock it back and forth and keep your fingers crossed, I have some D2 steering clutch parts if needed. The springs are available aftermarket. Replace the thrust bearings when your in there