The 2100 swap? Tons of folks have. There's how-tos all over the place about it (most aren't on here, people just link to them).
other than the adapter plate, you'll need to adapt the throttle cable somehow since it pulls the opposite direction from the stock carb (back, not down), I used a piece of aluminum scrap and a ball stud with a couple random screws.
Well I have been away for a little bit, but thought I would drop in and give a little update. I have been pretty busy with the "honey do" list and havent had much time to work on the Scrambler. Well I was able to get the adapter plate, and mounted up the MC2100. When I first started it up it had a really high idle, wouldnt go under 2000 rpm. I knew I had a vacume leak somewhere but just put it on the back burner until I had a chance to investigate. When it was running the throttle response was amazing though, even a poorly adjusted vacume leaking replacement was 100 times better than the gummed up stocker haha.
Well last night I decided enough was enough so I bought a rebuild kit for the carb and went to town. I found that the base gasket for the carb was the incorrect size and left a gap causing my massive vacume leak. I will throw her back on tonight and see if I can actually get the idle to tame down a bit.