You should be able to fit the 185 (precursor to the 200) or any 2 valve 200. The only years that definitely won't fit are 1984-85 200s. They have a four valve head (RFVC) and were similar to the 250s of the same years. In 1986, Honda went back to the 2 valve engine and has stuck with it ever since.
I think the 1983 and earlier XR200R had a differant off-set on the counter shaft sprocket than newer models. So that would mean the eng. and rear sprockets wouldn't line up. Check with BBR first they will know for sure.