Thermostat or No Thermostat?

Just for fun, what year is your 360 block? I understand that the early blocks (pre 75) had larger water jackets and thus thin cylinder walls. Just curious.
rumor has it the early blocks had thicker cylinder walls. I run the small , 5" ? , moroso aluminum drive pulley , stock 1970 340 radiator, mechanical fiberglass fan, no shroud and she runs at 180-209