Buyer Beware - Rick Ehrenberg

If there was enough moisture in that bottom end to rust pit those cylinders either prior to, OR after, purchase, that motor would've been locked up tighter than my pocketbook, the oil would've looked like a Sonic happy hour milkshake, and the cam and other associated parts would have blooming rust.
That rust damage HAD to happen prior to assembly, or after teardown, and if before so, the bore scope should've caught it.

That rust did NOT occur during storage

And regardless, the op STILL should've pulled it down to see what was in it, either before sale or quickly after.
I completely agree with this ,,,,,,

if those SEALED cylinders were somehow allowed to rust after assembly and before tear down , that entire motor would look like it was just pulled from sitting next to the Titanic. it was either assembled that way or sat outside without heads on it but with an intake covering the guts ???
OR
it's not the same 340