Hello Leon,
The cluster itself is from a 1965 C-10 with a 283. The tach is a reproduction I bought back in 2003. The vacuum gauge is from a 1967 Chevelle SS. I bought it off ebay in a stock knee-knocker pod from the SS Chevelle. All I had to do to mount the gauge into the 1965 cluster was drill two holes for the mounting screws.
Seth K. Pyle