Mechanically, that head will hook right on. There are a few issues where you might need to modify one or the other.
If you have a 89-90 model 9500, the faceplate angle on the combine in wrong (JD made a MISTAKE!) and it will tilt the head too far back. You literally can't "pick up" the head sitting on flat ground. With those MY combines, you have to have a wedge kit to roll the head forward. JD used to sell brackets for the head. I actually made a wedge kit on my combine to "fix" the angle problem. Wasn't a big deal) Later 9500-9510 combines had the angle corrected, and it just hooks right up.
Early 200 series heads did not have the lower hooks for the lock pins...you put several bolts thru the faceplate and header. Again, pretty easy to add brackets to the head if needed.
If your combine is has lateral tilt, you will need PTO driveshafts.
Hydraulically, the Reel drive hoses are on the opposite side of the feeder--may need to move them (or just stretch them across the feeder). I think you will need to remove the reel lift hose and replace it with a coupler. No big deal.
Electrically, if this head is DAM equipped, it may have a 9 pin plug or a 16 pin. You may need an adapter (JD), or to remove an adapter. No biggie. Early model heads had "AHC switches". Those heads had a 3 pin plug, and will need an adapter. Again, no biggie.
Things to look for:
Auger--bent or not.
Flex Cover plates-- rusty Steel or Stainless (preferred).
Is the groove the flex plates fit in on the back of the sickle bar excessively worn out? Plates may snap loose.
Does it have a bolt sickle (nice update).
Does it have poly on the skids.
Is the trough worn thru under the stuffer fingers.
Are the stuffer fingers good or broken off.
Reel--Wood bat, or pipe (update). How good are the bats.
Are the bat tubes worn down badly under the carrier bushings (reel may break).
Wobble box--does it feel smooth or is there a lot of play in the motion. Does it leak?
DOes the sickle bar shake back and forth (sign the A-frame ball joint is bad) If the sickle bar looks welded up, or the end skid with the wobble box looks new, it may be because the A frame ball joint is bad. A loose ball joint can cause those items to break in two bacause of vibration. The ball joint isn't hard to fix. Just need to know.
End snoots. Amost all of them are bent or dented a little. Make sure they float properly, and the frames are not a twisted up.
On the whole the 200 series heads were really good solid heads--but they have some age. If you find a solid one, it will work well for you.