Guess I'll chime in on the subject so I don't feel left out . I've got a 500" BB with A/C and the highest the (stock) gauge has ever gotten is half way on the scale. That was when it was 90 degrees, humid, in the city with the A/C cranked. The rad was built for me by a local shop (Glen-Ray Radiators) in the early 1990's. They used the biggest rad that came in an F/M/J body (360 with A/C probably), and added a 3 row core. With that, a clutch fan, shroud and Milodon hi flow coolant pump, I've had no problems at all. Also a high flow t-stat. Don't remember now if it's a 180 or 192 unit though.