Blowing out freeze out plug after start up

Hi All,
We have pulled the heads. Head gaskets holes matching up where they should. P/N's correct. Well everything has gone to a dead end. I blew air through the heads and block. My 2 other partners said they feel there is better flow through block and head. Hopefully dislaged something. Changed oil and filter. Decided to spend the 100 bucks on the gasket set and time. The alternative sucks.
The person that did the machine work said we overheated it and I obviously did not know what I was doing. Not a good selling point for me to bring parts back to him. We all feel it got hot but not enough to do damage.
Should have know the story next weekend, hope to drive it to his shop tell him everything was good, he needs to take a class on customer service, and do a big old burn out up the street........