Well I confirmed combustion gasses in the radiator last night... I had to run the car around the block a few times until it started to overheat and then vent the gasses into the overflow to test them. Interesting thing is I sniffed the fumes from the radiator afterwards and it smelled like exhaust fumes, maybe I came up with an unsophisticated test method... So, anyway, I guess I have to at least pull the heads and have them checked for flatness and tested for cracks.
The question is, with 116k miles what else needs to be done? I figure at least a valve job. I don't want to spend more than I have to, but I plan on keeping the car for quite a while yet. I really expected more from this car though