did you install the gaskets properly and TOQUE the manifold to specs in sequence? VERY critical. Make sure everything is torqued and all your vacuum hoses are reconnected then check for vacuum leaks. Check under the carb, pop the oil cap off and check that it isn't leaking internally. If all checks out ok I would check the choke and if it's still hard to start see if the fuel is draining down from the fuel bowl and loading up in the intake. The stock Q-jets like to leak. i usually epoxy the rivets.