Leaky Freeze Plug

They're not really 'freeze plugs'. Casting plugs or something to that effect.

Curious if you got a look inside at the water jackets and if it was now clean or really funky in there.

This sounds like someone ran straight water for quite a while.

 

That's correct on the name, they are casting plugs but everyone calls them "freeze" plugs so that's the name that stuck.

When freeze plugs start to fail from corrosion that's usually a sign of general cooling system corrosion. They fail before other components simply because they are stamped steel and thinner than some of the other steel components. I've seen freeze plugs out last the life of the engine and I've seen them rust out in a few years. The plug itself isn't difficult to replace at all but access to them can be a HUGE PITA.
You can put brass plugs in but they don't stay in as well as the steel ones. Back in the days of 7 psi cooling system pressures the brass ones were just fine. At twice that pressure the standard steel ones are a better bet.

The good engine rebuilders would always paint the inside of the freeze plug before installing them during a rebuild. Lay them on a piece of cardboard and spray paint the convex (interior side). Leave them in the sunlight for a few days to cure the paint before installing them. The exterior of the plug gets painted with the rest of the engine.

Sometimes you can come up with creative ways to get access to the plugs without completely pulling the engine out BUT if you do pull the engine - replace ALL of them while you have it out.