mate, you can put in longer springs if you want. In my '96 200, I put eibach springs to suit the XR400; a heavier spring to start with, and longer too at about 520 mm. I means that instead of needing that whopping great preload spacer, you can get your preload from a much shorter spacer. Now, I don't know if those springs would suit your earlier model, but have a yarn to any of the MX parts places or check the Eibach website for specs. I got mine thru Ballards.
I have also read somewhere that the post 95 springs are a good mod for the pre 95 models, but at .35 kg they are still soft...
Andrew