I've researched the topic here (great sight by the way) and read a lot about rear disc conversion. Seem like not too many of you are jazzed about this procedure due to the cost prohibitive nature, but if I could get cheap parts and decided to do it... Here's my question, Does a 91 or later swing arm bolt up to my 90 frame??? Sorry to bring this up again but I just wanted to be sure before I buy these parts. Thanks!

P.S. yes yes I love the drum brake but the liner is worn over size and I need a new hub anyway. Did you see what a new drum hub costs, Yikes!

According to my research, the swingarms are pretty interchangeable most years. The biggest problem in the swap is fabricating the rear brake master cylinder and pedal mount. Not a big problem if you have the equipment and talent and time.

You should be golden. Search for user ASF as he converted his 89 or 90 XR to have rear disk using a 650L rear swingarm and used a newer 91+ rear shock then swapped again to a 650L rear shock. The only "hard" part is the bracket fab and welding to the frame as stated earlier but that is still easy. If you don't have a welder or a friend with one then any muffler shop could easily do it for a couple bucks. I'd be even tempted to get all the other parts first and see if you can modify your current swingarm to work with the disk setup because it looks possible to me.
Good luck.

Don't forget the brake pedal needs to be modified too. I've got an 88 that has been converted. Pretty much as stated above. Can use all 600 or 650L parts.

Thanks guys! I work in a custom metal fab shop so that part won't be a prob. If things work out, I'll post some pics of the old hog with her new rear end. Thanks again.