Follow it through to the end!
My 83 KX500 came to me cause no one was interested in a KDX500, no one wanted a trail bike.
When i finally got to see the bike it was a KX, not a KDX, it just had a KDX seat cover.
In the end it may have turned out to be KX500 converted into a KDX at the time, but i'll never know.
As mentioned, if it is a twin shock KX, 1980 or therabouts, it is one very rare bike. Its worth the time to follow through and be 100% sure it is actually a KDX or KLX.