New carb for 1965 273 4-bbl hi-po package

On the hard starting when warm, don't disagree on the recommendations for a heat spacer under the carb, but have you checked your heat riser valve in the passenger side exhaust manifold? Could be stuck shut and sending virtually all of the right side exhaust through the hear riser passage in the head, underneath the intake manifold and out the driver's side. That will really heat up the intake manifold (as well as greatly restricting the exhaust flow). If it is stuck closed (the one on my 56 Plymouth was), eliminate the valve. In fact, eliminate it anyway unless you so a lot of really cold weather driving. Even better, pull the intake manifold and block the heat crossover, which runs directly under the carb. That will significantly cool the intake manifold and reduce fuel percolation after shutoff, plus generally add power from a cooler intake.