Jim - sounds like a great truck. I am working on my second 1961, so I will reply to your questions with what I have picked up.
The engine should be the grey color as far as I have seen. The valve cover would be the stamped "Chevrolet" one with the oil filler cap toward the front. I think most of the 235's were built at Flint, and I have always believed that the valve cover is painted the same. I am not sure about the Thirftmaster marking, but now I want to find this out. Generator question, yes, that is what I would do (my generator was replaced at some point and is toast now!) My data plate reads the same, and my engine is the standard RPO engine -- so is 95hp the rating? Again, I will see what I can discover on this. Great question. I am attaching a shot of some of the numbers from my 235. On base trucks, I believe the gas cap was body color.
Not much help, but you inspired me to answer a couple of these questions for myself. Best luck with your truck! GPK1961
