"Correct" meaning enough but not too much timing increases engine efficiency and reduces heat. Sure sounds like you were in the right ballpark with timing. Lean can make things hot as mentioned.

Usually hot at speed means inadequate radiator or radiator plugged. Could be other things but with a 2 core radiator of unknown? age and history, I'd consider a better more effective radiator. The Mancini "Muscle Car" 26" radiator with two very deep AL cores has worked well for me on a warm '70 Challenger. The 4 core Champion has worked well on a stockish brand F PU.