any year 200x front end will fit on 250sx, but you do have to redo the stops. The 86/87 looks a little better, because the stop cover is a piece on the lower tripple clamp, where the 83/85 the stop cover is part of the frame.
the 86/87 forks are also a little bigger with more travel. I have a set of each to put onto my sxs, I am going to do the 87 200x set first.
ATCnut
82 185s - sold
83 200x (hopped up)
84 200x (stock)
84 70 (lost this one to the DMV)
85 70 (soon to have lights, a foot brake, and CDI ignition)
84 200es (parts trike) - sold
85 350X (the best)
85 350X (siezed motor, dream of a poweroll kit someday)
85 250sx (frame was trash, got parted out)
86 250sx (the tractor)
86 250sx (a nicer tractor)
86 250sx (an even nicer tractor)
87 200x (parts trike, its really rough, a dog was chewing on it for a while)
87 250es Big Red (the tank!!)