340 with edelbrock heads overheating

That looks like an Oregon Cam Grinding sheet. They are very good, shouldn't have any concerns about them. Not that they couldn't make a mistake but not likely.

Sounds like you did everything to get air out of the system. Can't remember how many miles are on the engine but rings could be tight causing heat. Mine took over 1000 mikes to cool down after my rebuild. My guess it was a combination of air and rings.