Hard cold start- lack of fuel- UPDATED

I have a similar condition. My first thought is that the fuel is draining out of the carb overnight, forcing you to crank the engine to refill the float bowls before it will start. You say the carb has never been rebuilt... fuel could be leaking past old gaskets and slowly draining out either onto the manifold where it would evaporate or into the manifold where it would find its way into the cylinders and wash the oil off the cylinder walls if it doesn't evaporate first. My carb is a rebuilt Carter BBS 2 barrel so in my case I don't think its leaking past the gaskets... but I may pull the carb and re-tighten all the screws just to check. In my case, it takes several days of sitting before the car is hard to start.