Hy 50 sedan, Firstly welcome, now to the problems, a properly timed engine with the correct air fuel ratio, and a functioning cooling system should not overheat. A lean mixture will cause over heating, as will advanced timing. Is there a chance some sludge from the fuel tank contaminated your carbs? Did you time the engine with the vacuum line removed from the distributer and plugged? All the engine run on problems I have encountered were cured by closing the throttle as much as possible at idle. The last thing I can think of is not a pleasant one, could the engine be tight from a bearing or ring problem? How much vacuum do you have when you get it to run now? I hope some of this helps, good luck.
