I brush on boiled linseed oil to treat the wood in my Model A's. Be sure to use boiled linseed oil because it dries. Non-boiled oil remains sticky. I dye the boiled linseed oil with black enamel paint.
I found that the body fore-aft sills were treated, but none of the other original wood had a preservative treatment. The only treatment I found on the interior wood is body paint. Bill Cilker's original Victoria may have better evidence to answer your question.