Mine has air conditioning and at freeway speed would run right around 200 on the stock gauge with the air off. Got up around 210 or so with air on. I used a slightly modified P 15 radiator with a 3 lb cap and a recovery bottle made from a windshield washer reservoir. This was on days in the 90's with an electric fan set to come on around 180. I added an aux. temp gauge and the temps were just about the same. I did a lot of research on cooling, proper running temps etc. I got as many different opinions as I got answers. I bought a Walker radiator with built in AC coil and changed the electric fan to one with higher output. put on a 7 lb. cap. I noticed about a !0 degree difference. I personally do not think it was worth the extra money. In my opinion, these chevy's should be able to run 210 - 220 with no problems as long as you are not boiling the coolant out of them. I have to state that I haven't done any mtn. driving or climbing, so I don 't have a clue as to what this would do to the temps. BTW, I run 70% water 30% antifreeze and 16oz of water wetter in mine. Hope this helps, Good Luck, Geoge