I think you're on the right track, but maybe the wrong order. I would look at fan, pump and then radiator. You know your four blade fan isn't enough. I'd replace it with a five blade and a MP viscous fan clutch. If that doesn't solve your problem, look at replacing the water pump. I used a HD for police and taxi applications. If you make it to the radiator step, take your's to a local radiator shop and have them check it out. If your car is mostly stock, it should be fine after it is cleaned out or maybe recored. I bought a four core Champion w/dual electric fans for my 67, but it is a cut up hot rod, not a mostly original car. That's just my opinion.
