It is unlikely that an iron head would warp, but possible. And I scraped the entire head surface with a razor blade cleaning it up, and noticed no cracks at all. I guess I'll find out, because I will be doing an "autopsy".
The cylinders are emmersed in the water jacket. I saw that when I replaced the water pump. If the water level got low enough, on an almost 50 year engine, a hairline fracture could develop into an honest crack. Especially if I introduced cold water into the system trying to bring the water level back up.
This is what I think happened. And that is a mistake on my part. I should have probably let the engine cool slowly, even if I had to abandon the truck on the highway and replace the water pump on the side of the road later.
The motor could possibly be resleeved, but I don't know that I would trust a compromised cylinder.
However, yes, I am set on something else...as Cletis says, a "real truck engine".
292's were installed in "real" GMC's in the 60's, I believe, and are often listed with other GMC engines, even though technically, I think it's a Chevy. Isn't that right?
Like I said though, after the autopsy, everything good will be sold to help finance the bigger stovebolt. Block (if salvagable), crank, rods, pistons, the new water pump, the head and valve train, intake and exhaust manifolds.
