The gaskets in question are 'supposed' to be put on or 'are' installed? If the original gaskets are fouled or have tears it will be an issue straight up. If the auto choke butterfly is in a near completely closed position on start up then I'm gonna say there's a vac leak in it somewhere. Other option is the air/fuel mixture screw is set incorrectly. Make sure the mounting bolts are on firmly and give the base of the carb a liberal squirt of WD to see if the idle fluctuates. Check other places where a leak can take place - brake booster line, all the small vacuum hoses and check the inlet manifold nuts to see if they're tightened sufficiently. Vac leaks can be a bane to hunt down. If all is good then 2 pumps of the pedal and throwing the key over should be all it takes to start the engine.