[ford38v8]

Woodie, To be clear, unless you have a restrictor valve on the exit end of the overflow tube, It makes no difference what cap you use, you won't have a pressurized system.



Radiators of the day were not designed to be pressurized, but yours is of a design that will readily accept 3 lbs pressure. Your choices are simple:
1 - leave it as it was built.
2 - Install a Skip Haney 3 lb restrictor on the overflow tube and a pressure cap.
3 - Install a coolant recovery system as has been described above.


To help you make the right decision, remember the phrase "If it ain't broke, don't fix it".