I have removed the heads on my 1998 GMC Sierra K2500 6.5L turbo (135k miles) after having problems with loosing coolant and fluctuation of the coolant temperature typical to a head gasket failure. I also had bubbling in the reservoir even after extensive tries at getting all of the air out of the system. I had no signs of coolant in the oil and the truck was still running great.

I'm looking for some direction as i have the heads off and the head gaskets don't appear to have a major failure between any of the coolant passages and the cylinders themselves. I was expecting (almost hoping actually) to find a blatant failure. The bottom of the cylinder heads and the mating surface on the block are in very good condition.

This is the first time i've removed heads and figured it would be worth the money to take them to a shop and have them cleaned and inspected for cracks. I haven't cleaned them up yet to inspect closely myself. Are there any particular areas in the heads that are prone to crack that i should inspect? I live near Iowa City, IA and would be open to suggestions for a reputable shop.

I've done tons of research and searches on this site to get where i am now and am planning to install new injectors and glow plugs upon installation of the heads. Any additional help would be greatly appreciated!