When I added my h/c/i a little over a month back...I put on a Griffin Radiator and 180 thermostat with the added power (usually causes more heat)...on my stock guages it used to read a little above the "centerline"...but now the guage reads at the top of the "L" on NORMAL on the guage...it runs real cool when on the highway...
on my 93 i replaced my stocker with a fluidyne radiator and my temps dropped from 195ish in stop and go traffic with the a/c on in 100 degree texas summer to about 185.
stock fan/clutch, water pump, and a 180 thermo.
i don't have a/c and i will be putting a 160 or 180 in there with an electic fan in texas also. i want to put an oil cooler on too so i can cool the engine even more. so maybe i can get cooler
a proper and efficient cooling system should maintain a constant temperature, in our case, the temp specified by the thermostat. A failing radiator will not be able to keep up with the thermostat, therefore, a good flowing radiator should keep the system at a constant temp, in our case below 200, or right around.
real world answers, it never goes past halfway, and I'm in cali.
my brothers 86 has a fluidyne, and he's never had a problem (stock engine though)
for his other car, he was on a budget and went the autozone route, autozone has a super cool oem replacement radiator. a 3 core for only $180
radiator p/n is 433138
It works so damn well, it never goes past the second line on the temp gauge, here are some pics. this is a great budget cooling install, that still looks good.
My Ron Davis dropped it a good 10 degrees on my Autometer in 90 degree driving over the stock one. What really made the difference though was the Edlebrock Victor H20 pump- I think the stock pump was my real problem not the radiator at all, even though swapping the rad did make a difference- but the Victor is what seems to keep me from overheating now in stop and go. Ramcharger up next, hopefully then I'll never go over 200