My '65 Mustang coupe has a 289 2bl w/ automatic trans. & original air conditioner. The original 3 core radiator checked OK, I even replaced the thermostat twice, water pump checks out OK and the block was flushed out. It still has some cooling problem on a hot day(75 +) or slow traffic. It has the original 5 blade fan which is approx. 2" from the radiator. Would a 6 blade fan improve much, and should I space the fan closer to the radiator? Would a 4 core help and how much?