Electric reverse flow pump and plumbing lines right to the heads like the photo of 73Swingers' has got to be the best fix of them all. Fresh coolant right out of the radiator to the hot spot first. That extra flow is really needed on a gas burning deal with two cylinders exhaust being right side by side from the valve seats to the outside of the head. Not nearly as much coolant can get there as the next best spot which would be the end of each head. Where the intakes are paired, I'll bet the temps run several degrees cooler than the average.