On30, eh?
Now that's thinking outside the box! (Punny!)
As for reefers...
Really, about all that would be needed is some reefer "hard ware" (door paraphernalia) and using Evergreen styrene for sides, an appropriate 027 shell could be hacked and used for 36' wooden reefers. 36' reefers were still plentiful in the late-40s/early-50s.
Andre