My 62 firewall was interior cab color. That surprised some folks as most are painted truck color. I never did find the reasons. My guess is that some plants just painted with what they had in the gun. I like the fawn collar on the firewall and I am considering what I will do with my 66 cab.
By the way - time and money goes with a new cab. You will spend quite a bit on panels, and filler on those holes.
