New Interior Paneling
I was going for the look of Birch, but couldn't find any locally, however, I did have a friend with an old lumberyard/millwork shop (the place had been shut down for 20 years, but it was his "hangout").
He had unused stock from the 50's (and likely before) that he provided. The paneling is 3/16ths thick, and so closely resembled Birch that it was an easy choice.
He also provided much NOS polished aluminum trim that was perfect for the new interior!