5.2 and 5.9 have the same head. There are a lot more 5.2 than 5.9 motors.

Me personally Ive had 12-15 vehicles with 5.2/5.9 motors and as yet not had one have a prob with the heads.I have a friend that works at a machine shop who claims to see it frequently.

I have however, had to fix the plenum gaskets on 5 or 6 and sometimes I think this is an useen factor to failure.When it goes bad it sucks oil out of the valley and into the intake manifold and is sometimes hard to detect by people who don't know what to look for. People just run them low or out of oil and burn them up, or when the gasket goes bad they run lean and detonate and people continue to drive them in disrepair.

3.9L dont seem to suffer these problems as much.