I've not found a kit, but I usually just fabricate my own. Adapting skis to the post is one of the easiest mods you can do on a sled. I have a set of aftermarket skis that were meant for a 99 Cat on a Skidoo Touring. Just took a few spacers and made plates (bolt holes are larger on the skis).
That said, the Pilot skis might be a bit over-keel for that 87. (like that play on words?) The keel on the bottom of the pilot ski is about 1" deep. That 87 may end up putting to much pressure on the skis and might not be able to adjust out of it. I'd bet the height difference including the keel is close to 2" from the bolt hole to the bottom of the ski.
That is a lot of adjustment for a suspension.