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.
2015 Skidoo Renegade BC 600 Etec
1999 Skidoo Summit X 670 HO (Son's)
1996 Skidoo Touring E 380F (sister's)
1995 Skidoo Summit 583 LQ
1985 Skidoo Tundra 250F
1999 Arctic Cat Jag 340F
1999 Arctic Cat Z 370F (son's) - needs track
1990 Arctic Cat Jag 340F
1982 Arctic Cat Panther 440F