Water intake nipple corroded
The motor is now on my stand in the garage.
You will never have easier access, though this is a fairly accessible area with an engine in the car, and not too difficult a job. If the pipe collapses as you try to turn it, that will just make it easier to fold in, which makes it looser. Worst case, you could drill the pipe until the walls are thin, then fold it in with a chisel. There is a plumbing tool which grabs the inside of a pipe to let you turn it with a socket wrench, but don't use that if inside the head since it expands the pipe.
Wrap the new pipe's threads with teflon tape or coat with gasket sealant or pipe dope. That will make it much easier to remove in 30 years. If you must replace the short water hose between the head and water pump, buy some silicone heater hose as it is much more flexible, so you won't spend an hour trying to work the hose in, and lasts almost forever.