In the case of #65 there was very little left that was sound enough to save. Our original plan was to reuse some of the wood in the frame and one side wall. Very early on this was determined to be rather impractical, and since the car was intended to be operational the decision was made to replace the entire frame.
Keeping the body intact allowed us a "solid reference" to referto as we were building the new components and reconstructing the platforms etc.
It would be possible to seperate frame frome the walls or roof from the walls or remove a wall for heavy repair or replacement. I belive Durango has replaced the frames on one or two of their old wood cars. But it would be a lot of work.
I would reccomend anybody considering such a project plan to take far longer to do the work than you think. Doing the actual cutting and fitting doesn't take that long. It's figuring out how, and most importantly, why they did it that way. So much of the knowledge that went into building wood cars died with men that built them.
Another lesson to learn is to keep those wood cars inside and protected. While there are subtle parts of the design to keep the water out they can never be completely sealed.
Paul