The last time I think you could get oil injection on one of Kawasaki dirt bikes was in the 70's. I had a 1975 model kd175 that had oil injection. It even had a rotary valve engine where the carb was on the side and it was very similar to the small street 100 Kawasaki makes now. For the mid 1970's the kd175 didn't do to bad in the dirt. It would be crude compared to the new kdx.
Im a SR owner and Im really happy with injection system, just top her up and she runs feel fine (you know what Im talking about Ede). :think
The differences in the engine department are a little involved to allow you to convert a standard KDX. The oil pump sits on the engine casing under the carb area and drives from the rear of the clutch housing. The throttle cable is a dual action affair to open the oil pump with the carb. This would mean having to machine an opening into you engine casings, create the gear work to be driven from the clutch. The oil tank sits under the tank which I think is the same as on the KMX200 (actually while on the subject the SR model is somewhere between the KDX200 and the trail/road KMX200).
The carb is also smaller being a 28 or 30mm unit which helps the pump fit underneath it due to its smaller size, the airbox rubber mouth then is smaller to match.
Id say that IMHO you can't do a convertion, you'd be better finding agrey imported SR model and either use the engine or stick with the standard KDX.
performance wise, I don't see any real difference as Ive rode with the 'ordinary' KDX and can't find any benifits.