When you say "hard cranking" what do you mean?

If the static ignition timing is just a little too fast the starter may make a "grunting" sound while trying to crank the engine. If it does this, retard the timing just a little until it will turn over easy.

If it cranks fine but simply not firing up then could be carb is flooding the engine while it is sitting. Is there a thick gasket between the intake manifold and the base of the carb? That might help a little with heat transfer issues to the carb.