There is not a whole lot of advantage of the rear suspension from the KX. Pretty much the same. YOu would be better off seding the shock to get revalved and swap the fluid and new nitrogen.
For the front, you need the complete setup. Wheel, hub, axles, brakes, tripples and forks. Then press out your steering stem and into the KX unit. Do some research to make sure they take the same lower stem bearing. That should tell you that you have the same diameter on the lower clamp. From there, bolt it on.
The KDX250s also had inverted units at 43mm and I know they and the 91-95 KXs use the same 32006 lower bearing. Also the 93-94 200s had 41mm inverteds, kind of odd units for inverted forks to be honest.