[Zenwren]

I just picked up a 95 k2500 from an elderly neighbor, 454, 80k original miles but it appears to have been pretty neglected. I know he had the water pump replaced recently and probably hasn't taken it on more than a 15 mile drive for years. The coolant was NASTY so I flushed it a few times but it seems to keep turning from clear water into sulphur smelling mud color. I noticed a small (think carbonated beverage/champaign sized) stream of bubbles coming coming up through the funnel while I was bleeding air from the system and decided run one of those blue water combustion gas testers. Sure enough it turned yellow right away. It doesn't seem to ever get hot, blow smoke, or have coolant in the oil. I'm guessing I have a very small head gasket leak? Is there anything else I should check before I tear into this thing or is it pretty much a done deal once it fails the test?