No real difference if you couild do an apples verses apples comparison. The head had the non cross flow exhause heat to add to the normal duties, and short intake tracts with small bores and I guess the peak temperatures are the same, but the time taken to heat up is more than aluminum.
The head is designed around a very small intake runner, about half the detachable intake volume, and non cross flows should run hotter at the intake, but the thermal process is tuned to provide target air fuel ratios, and Ford's later versions with detachable intakes ran much higher compression ratios without detonation, but that doesn't mean the iron head intake tract is the culprit.
If someone recast the aluminum intake in cast iron, you'd still then end up with less intake heat because its so much bigger in volume, and would have less heat soak.
Some years, the short intake volume helped Fords emissions (like the 1978-1980 engines that didn't need an air pump in all states), some years (the thermocator years from 1967-1969), it was a negative.