Ask him to give you the two digit code that is cast into the roof of the center exhaust port runners. That will positively ID the heads and give a much better idea of whether his asking price is reasonable.
Here's a pic of a 6X head, almost every Pontiac head has two big letters/numbers in the same place as the 6X on this head.
Treat any non-running engine purchase as if you are buying a core engine that will need a complete rebuild.