472 Hemi in a 68 cuda ,cooling problems

do you have undersize(race) pulleys that reduce the fan speed? they would slow down not only the air movement thru the radiator ,but also the amount of coolant flowing thru it?

I have done several Hemi A body swaps....all with March pulleys that are standard ratio....never a cooling problem in the 100 plus degree summer heat....with the A/C on.

A simple check....does it cool down when sitting still , but holding the RPM around 1200RPM?....if it does....bingo!