Uh, yeah. The later tank will NOT work w/ the '87. There is another thread I've posted in ('87 KX 500)and explained the differences. Unfortunately, the big IMS "lump" is about as good as one can do for a replacement tank, I think.
The later shrouds will work w/ my IMS tank. The holes line up and everything, although I didn't have the pipe on the bike when I fit-checked them. I suppose it would be easy enough to trim them to fit though.
I also bought the seat w/ that tank, and it isn't of much use either since the tank won't work. The seats are particular to the early and later tanks. Hmmm, any body looking for a tank and seat?
It's primarily the hairbrained way the upper subframe mounts which prevents later tank usage. The aft tank mount isn't much of a problem to work around, but altering the shape of the tank or altering the upper subframe mounts........well, umm, not worth it.
I don't know if I've mentioned this anywhere else, but be diligent in comparing your part numbers. When I handed a list of numbers to a parts guy at my favorite dealer, he checked off many of the numbers as unavailable, according to his Kawasaki software. These are parts like suspension bearings that even the aftermarket doesn't support. I started comparing the '87 fiche to later models........even the '04s, and found that many of the part numbers are identical, and have ordered them against a later model year w/ no problem. Go figure. I haven't yet installed any of these items (customer bikes and other obligations taking precedence), so I can NOT confirm that they are indeed the same, but if they aren't, Kawasaki has some issues to rectify in their engineering support department if they're applying the same number to multiple parts.
In addition to the later KX500s (for compatible parts), I have also found that the KLX 300 and 400 share many of the same parts (wheel hubs for example). Of course, the '87 250 shares quite a bit too.
For example, the bores in my hubs are shot, and the hub assembly part number came back "unavailable" for the '87, but I can buy hubs for a late model KLX (w/ the same part number) all day long.