Depending on how the coolant was maintained, it's not un-common to find the front intake manifold water passages eroded by electrolysis, and material will actually be missing/eroded from the alum intake, requiring some welding.
^ This. Think about how many super corroded water necks you've seen at swap meets and pic on the web. They make radiator caps with a sacrificial zinc anode for winter storage. Most coolant has corrosion inhibitors, but it needs to be freshened every few years, like 3 max.