I ruined an engine once with a distributor that had advance problems. Static setting was fine, but there was waaaay not enough advance at speed and it overheated all the time, finally I burned valves and piston tops from the late flame front rushing out the exhaust and not put to work expanding (and cooling) as it pushes the piston down. Power felt fine and there were no other tractability problems.
It was the engine that got me to sit my butt down and actually learn about ignition advance :-) Expensive classroom!
You don't need to get too fancy to check the distributor, it's easy. With static advance set, keep the timing light connected. Pull the hose off the distributor and rev. it up. Advance should increase 10 - 20 degrees (depends on your motor). At idle, suck on the host/apply manifold vacuum. Advance should increase 10 - 20 degrees with vacuum. If those things don't happen it could be a source of great heat in the cooling system.
Most motors are happiest with ported vacuum, but you might try full vacuum on the distrib to see if that affect at-idle overheating problems.
I'm assuming your cooling system doesn't have a problem.
By the way, I just had the radiator in my (inline) station wagon. Rad was new in 1996, developed a leaky around the top hose. Took to the local radiator shop to see if it should be repaired, or replaced. Simple fix, but he also took the top tank off and rodded it out.
Man what an improvement! I maintain my cars top-notch, but "calcium" or something does build up in the tubes, and the car runs noticably cooler. (Meaning, runs low-normal in hot highway, instead of hot-normal on th gauge.) $65 well spent.
