That intake and carbs are worth yeah, $300 or so. I would sell each carb and the intake alone, not as a package deal. Put it on E-bay and sell them.
Water does get in the cylinder when the heads are pulled. No rust means the water just got in there.
You did not prime the motor and started it, so you don't know how it would have ran. It still was a used motor, right ?
BTW...I was not the seller