I'm running 100/90 front and 110/90 rear in a bridgestone BT45
Replaced the classic michelins, and the bike handles so incredibly different it's amazing. IT leans and feels very nimble now. I have only ridden in light Darwin rain but the tyres felt very good. (Light Darwin rain = heavy Melbourne rain, we can get 200mm/hour at times here in tropics)
Theres about 5mm between the swingarm and the tyre, I wouldn't want to try the 120/90 on the rear I don't think there would be room.
My bikes '81, twin shock.
John