I can run my AC in traffic without overheating on my 400. NOTHING special, didn't adjust the water pump divider, stock 19" clutch fan, 180 t-stat, stock radiator with trans cooler, currently running stock distributor with points. All the metal baffles and valence are in place, although I can't find any sign of the mysterious masticated fillers So I think the baffles are important for increasing the fan's efficiency at low speed. I agree, check your vacuum advance and distributor mechanical advance for proper operation, and the advance curve to make sure it's coming in on time for your gear ratio.