On my 65 with AC there is a valve that regulates how much vacuum the water valve gets. Not sure if non-ac cars have that feature but I don't see why it would make a difference to the water valve.
Only other thing I can think of is the hose size from the valve to the core may be different.
Putts drives a 1965 customized Galaxie. Rebuilt 390, 4100 electric choke on a Performer, MX, AC, PS, PB w Scarebird front discs on Cragar 17" S/S.