I am a firm believer in having the intake and exhaust bolted together in their final position. I have been truing them as a unit on a belt sander for 50 years and haven't missed one yet. I have seen the intake and exhaust milled separately only to discover that the mating surface of the two manifolds was warped and the guy who spent money to have them milled separately still had leaks. I also have fears of milling 60 year old cast iron. I have seen it shatter.
