Duane Habets of Conrad, MT sells a kit of the 502 air tractor. PM me and I will give you his email and phone number.

http://www.designerimages.net/pages/...ir_tractor.htm

Duane has sold over 20 of these kits. Recently I have been doing the wing sheeting and capping for him. You may have to wait a bit, as he recently has started a new business with his son that is occupying a lot of his free time. But believe me, it is worth the wait.