The shock from an '86 to '91 would be the best years of the shock. The most common upgrade to the forks are CR forks with the disc brakes. In '93 they chopped the suspension to open the XR market to shorter riders.
I do not want CR forks because that would mean reconfiguring the whole front end, however I would like to know why an '86 to '91 shock would be better. The 200s from '81 to '85 seem to sit up higher and have a smooth suspension. I have not riden any XR200s from '86 to '91 so really I don't know. What are the benefits of the shock you suggested?