I've got a 240 kit (72.5mm) in an '83 and I'm converting a '88 to 240 as well.
Used barrel, a used piston from the '83 and a new set of rings.
I don't remember what jets are in my '83 but I'll have to get into it with the '88 as it's a standard 200 at this point.
Look after that piston, you can buy rings for them but getting a piston (they came in 72 72.5 and 73mm) is an impossible task as any rare kdx part I've sought.
Standard 200 carb is 34mm 300 main 35 pilot from the service manual.
In relation to the power valves, I adjust the valves to the rack by eye. When you do this it very obvious when it's right and it's simple to do.
The Kawasaki manual I have has this timing listed incorrectly and it took me ages to accept the manual was incorrect.
Love the 240, can't go back to 200cc !