The impossible to solve overheating problem

one thing to check would be ign timing just because you turned the dist doesn't mean the timing is advancing the weights could be rusted and not moving, is yours bored .060 over because mine would heat up really fast in the winter but in a truck with a large radiator it would run 200 in summer with a 160 stat but run 210 when towing and that was with everything stock and new radiator also had problems milling the heads that low all the cylinders cracked between the spark plugs and intake seats.