cracked cylinder head question

[speedfreakracing]

Hello,
I have a 2000 Pontiac Grand Prix with a 3.1L V6 engine. The guy that had the car before me replaced the head gaskets and put the pushrods on backwords causing a bent valve concern. I pulled the heads off and found cracks between the valve seats in the center of the combustion chamber on all cylinders and some cracks from the valve seats to the spark plug holes. I bought a set of 3.4 heads from a 2000 Chevy Venture that were machined and the machine shop said they were good to use to replace the heads I pulled off. One cylinder head doesn't have any visible cracks and looks good. The other cylinder head has one crack between the valve seats in the center of the combustion chamber (thinnest part). Is this normal to have a crack in this area and is it ok to use this head or is this head junk? I didn't find any other visible cracks on the 3.4L heads (cylinder heads are very clean). Any advice would be greatly appreciated. I know some cracks on diesel heads are normal but I find it hard to believe on a gas engine.

[speedfreakracing]

Picture is added of crack, I used a pencil to help point out the crack.

[86FieroSEv6]

Just say no to crack.

[SappySE107]

Its junk. I won't use any of these heads with a crack, leaking or not.