Summit has a gasket set for Intake Manifold for $36.95. You could spend that much doing a couple of oil changes.
Guess it depends on if you want to gamble on blowing the engine. With the amount of water described, it is most likely a intake gasket with the coolant flowing through the valley and into the oil pan.
If that much coolant went through the cylinder, you would expect it to hydro lock.
I just can’t see doing major damage to the engine because of a few gaskets. Then again, maybe the truck is not worth saving and buying a few weeks with a “gasket sealer” tonic, is the answer.