To summarize the changes to the 250 over the years, unless you have a Franken-motor:


If you have a 250 with a non-integrated head, with a separate intake manifold, it is likely a 1974 or earlier car or truck 250. But it could be a 250 out a 1979 Camaro, Nova, or Caprice. If it still has the original engine paint, the 1974 and earlier were Chevy engine orange and the 1979 was GM Corporate Blue (a robin's egg blue, not the Chrysler blue they sell in the spray cans marked GM). I don't know if they 1979 valve cover was different from the earlier one? The main difference is the exhaust manifold, as the early motors had and angled 2" outlet while the 1979 had the exhaust manifold off the SD truck 292 which point down and was 2.25":




In 1975 and 1976 cars and trucks, they introduced the integrated Monojet head (along with the catalytic converter in cars). I don't have any real good pics of the head itself, only this one below. The engines were Chevy orange and had an exhaust manifold with a 2.25" outlet that pointed down for the pipe to run under the oil pan to the passenger side (it might be the same exhaust manifold as the 1977 and 1978 integrated). The valve cover is unique as it has an extended portion at the base that covers an additional oil gallery on the driver's side:




The 1977 and 1978 used a second version of the integrated Monojet head. Sometime during 1977 they switched from Chevy Orange to GM blue. The valve cover is similar to the earlier integrated one, but now lacks the side extension. The replacement valve cover gasket that Felpro offers for both these heads is made of cork and has the side bit for '75-'76 which you cut off to fit the '77-'78, so bolt pattern is the same (this one is mine of course):



[img]http://i.imgur.com/E7tjdva.jpg?1[/img]


This in 1979 to 1984 250 trucks they introduced the Varajet heat with its unique two barrel integrated manifold. It was GM Corporate blue until they introduced the engine black, which I think was '83 or '84? I'm not sure what the bolt pattern on the valve cover was like. It also had a unique exhaust manifold that had dual 2" outlets, although it was all one manifold inside and out. The factory exhaust actually just went a little ways and had a Y pipe into a single exhaust.



[img]http://i.imgur.com/4zf0574.jpg?1[/img]