For clarity...

Two days ago, it ran perfectly fine. Went for a ride and runs poorly upon return. Tried a second distributor, and it likes 30° initial timing. Idle vacuum is 10" at 1000 rpm.

Correct?

Couple more questions: 1) How do you know or confirm that it is not a vacuum leak? 2) how big is the cam... did it always idle with 10"?

If it ran fine one moment and then not.....something has changed

When was it in for leak repair?, and why was it overheating?
I cannot help but think that there is more to the story that would help diagnose the problem. Maybe a little more history on the car.