How are you deciding what pressure cap to run on your radiator Thanks

18-21 psi, got to keep the coolant in the radiator.

From memory, 12 or 14 psi was original and some replacements are 16 psi. With a good cooling system + antifreeze, either should work fine. Boiling point with 50/50 is above 250 F with 12 psi.

Only thing to add is sometimes the "flip top" type with pressure release lever tend to leak. I avoid those. Otherwise I find a decent replacement cap from the AP store is fully functional.

If you want original appearance, need to look around.