340 Not firing on all cylinders

you mention "the distributor moves very freely". It sounds you might have moved it when you switched the wires and it's not starting now since the timing is off. Make sure you reset the timing (10 degrees before top dead center is pretty safe for initial timing) and that the distributor is bolted down properly.

What type of carb do you have? On an Edelbrock the vacuum hose goes on the ported side (passenger side) of the carb.