The aftermarket intake is questionable , as i have had 3 bad ones 4th. was acceptable . Turn manifold upside down lay intake gaskets on , align to the bolt holes and see what you got . The 1 side was good the other was terrible as the gasket parting line from port / port was into the next port by 1/4" . That is the approx. distance between the ports to begin with , the bolt holes were fine . Most people lay the gaskets on the head , drop manifold from top , done . Line up the gaskets on everything . As for the carbs. make a set of block off plates for the end carbs start engine running off ctr. carb. only . If it runs good then add the end carbs. if starting to run worse end carbs. are pulling air in through the throttle plates , must be sealed or you will have low vacuum etc.