Noticed the difference in the intake manifold gaskets as one has openings for the exhaust crossovers and the other doesn't. Early 67 so no large valley pan. I know exhaust blocks have been used to fight vapor lock. Heat riser for choke depends on hot air. So what are the pros and cons? Thanks

 

There are two Turkey trays, early and late, the cross over is larger on later heads. There is just the side rails style in steel from Feel Pro for your motor. Plugs come loose and a piece of stainless steel or the heads cross overs filled are needed with gaskets with no cross over cut out. Otherwise they just burn through the fiber gaskets.