Question...what is the normal running temp for a 1972 340

X2 on this

"Your running cool at lower rpms so low speed operation of the fan is probably working. At higher rpm on the highway the fan may be turning to slow.
High flow water pumps sometimes cause cooling problems due to coolant moving to fast thru the radiator. ie not enough time for heat transfer. "

When you shut motor off that fan should stop rotating within 2 or 3 turns.....If it keeps spinning the clutch is shot.....replace....could be slipping......that is the only thing bad about clutch fans versus direct drive fan.....

Do you have an 8 blade fan on there already?