one sugestion:
check your total timing, if it is advancing to much you motor will run hot
should be at like 34-38 degrees at full advance oh right to check your total timing, leave vacuum advance hooked up and just check the timing while you slowly raise the rpms until the timing stops advancing
my friend had an overheating problem like yours, we checked he was 8 at idle and 54 at like 2800rpm, changed distibutor and problem solved