You might look into a preservative which soaks in, while leaving the wood open to breath. I'm not an expert but it seems painted wood rots almost as fast as raw wood...paint holds in moisture and wood needs to vent, expand & contract.
There's a ton of choices in stains & oils when you talk to the wood experts.
Like you I've also considered reusing most of my original 31 body wood...at least I know it fits. The roof bows are rotted, but the door pillars and wood around windows appear very sound.
When I first got my Model A the interior was gutted...gone...just a the seat springs, but that old thing had a wonderfull aroma when you sat inside.
The closest I can come to that smell is going inside certain "antique furniture stores" which are using linseed oil on their work. I love that smell....it reminds me of my old car before I took it all apart so that's what I plan to use on both the old wood and whatever new pieces are needed.
Has anybody here used Linseed oil? (inside a car)
Boiled or raw?
Did it stink you out?
Would you do it again?
Inquiring minds....