While rebuilding my brake system on my 74 Z28, I see I have an Iron combination valve that I am accustomed to seeing on later 2nd gens. Resto parts houses sell brass versions for this year. Is the iron combo valve similar to pictured below correct for 1974? Or was this swapped at some point and it should be brass?? I see Musclecar research is a good source for parts and hopefully they have all the internals needed to rebuild. I just don't want to bother if this is not the right valve to begin with.