No KDX250s came with a front disc. The 200s didn't get them until 1986 - easiest ways to pick the later 200s from the earlier bikes, are the safey seat and KIPS exhaust power-valve.
Can't think how to describe the differences between an early 200 and a 250 (not that I really know them properly anyhow). Both had the same style of Uni-Track rear suspension (similar the the Full Floater set-up of the same era).
To work out whether its a 200 or a 250, the best bet would be to look at the barrel for the capacity. Compliance plate will also also tell you.
The 250 was a very good bike in its day - always got rave reviews. Like the PE250, it suffered by not being updated regularly, so the IT edged ahead as the years passed.
Among the Jap 175/200s, the KDX200 was always the best or a close second.
Either way, they're supposed to be a good thing to ride, and ought to make a great Vinduro bike.
Kawasaki parts are far harder to get, than I've found for any other Jap brand. Admittedly, I haven't gotten too serious on chasing bits for my KDX200B1, but when you walk into a Yamaha dealer and ask for parts for a 1968 model, they'll at least try for you.... Unlike my Kawasaki dealer who pretty much refused to acknowledge that there ever was a year 1984, and even if there was a 1984, nobody was making dirt bikes then....
Plastics are a particular bitch - 'nobody' seems to make old-style universal rear guards in green, and definitely not with a tail-light on them.