I had an '82 GMC 1/2 ton manual trans with a 250 six and the integral manifold head that developed oil in the water and water in the oil (butterscotch stuff clinging to the oil stick) But it never lost any oil from the sump or water from the radiator.
I was only driving it a short distance daily in a high humidity area (New Orleans) and almost never long enough to warme it up. And it still was running fine. Although I swapped it out for a 283, I always figured that condensation might have something to do with it.
