radiator cap recommendation

[roadking]

im still a little confused to what the proper radiator cap to use, i have stock crate 350 non-a/c and no recovery tank with a new 4 core modine raditor . im currently useing a 13 psi cap, under (hot condition) and i get just a few drips of anti freeze out the overfill hose, ive also ran a 16psi under (hot condition)i have no anti freeze leaks but i feel i may be over pressurizing my system? sometime in the near future i will be adding aftermarket a/c. what is the correct cap recommendation for non a/c and with a/c systems? thanks


note: (hot condition) 95 degrees plus humidity