AutoX gearing, 20” rear tires gearing question

[BWard]

Finishing wife’s AutoX build, trying to figure out gearing, we’ll be running 20” rear tires, this will be a trail rider, fence checker for us. what are you all running gear wise for your AutoX?
Also how many link chain?
Our motor is a 86 200s on a 83-85 200x frame.
Thank you,
BWard

[RapidRick]

12-13 tooth

[BWard]

I don’t think there is a 13 tooth for a 200s, JT has a 12