My '66 has a 289 with some engine mods and an HEI ignition. Looks like the recommended plug is an Autolite AP45. I pulled the plugs and the engine has Autolite 24's which it appears is recommended for later model 302's from what I've seen. Would there be a reason someone would have installed the 24 vs. the 45? The ignition?
FWIW, the engine does run hot and it seems to run rich, though I pulled a plug and it looked very light tan, like it was running lean. Pic attached.
So which Autolite...

289 Spark Plugs Recommendation