When I was doing a '34 Chevy Sedan, I found there are few companies out there that make reproduction interior wood kits. Whether or not you can find somebody that has a kit for your truck I don't know.
But I found more people than not are using steel to frame in these bodies. Is all the wood there? If it is you could try building them yourself, or it would atleast give you an idea where to build your framing.
If I can dig up some info on the wood kit companies I will, but I sold the car a few years ago.