How do you know if you have "enough" radiator?

I bought a 2 core 1" wide cores aluminum for 125 online for my 360 no shroud the cheapo blue flex fan and it stays plenty cool actually had to put in a high temp thermostat to make heater and defrost work better lol now it stays right around 150-160 even in stop and go traffic it was at 100-120 with old thermostat