If it were I, I would get creative on my own as the trucks of those days really didn`t have a interior. They just had the very basics thrown in.
I imagine also riding in these with a V8 transplant makes the interior even worse noise wise than it was new, so adding some damping material would likely be of help. The older cabs like that had so little damping in them you can talk in them and hear a small echo. Really blew my mind the first time I noticed it. Your truck, you decide. But in case you can`t find what your looking for, get creative. Diamond tuck seat, door panels, would look old school but never goes out of style.