[Brian T]

In addition to what Paul said, invariably some junk will fall into the water jackets and cylinders, when finished cleaning wipe some grease on the cylinder walls and crank the engine over by hand then any dirt will stick to the grease and can be wiped out.
When the head is on and plugs installed, I flush the block by removing the water inlet and flush down thru the outlet to remove any gasket particles which would end up in the radiator.
I see it mentioned often that Graphite gaskets are difficult to remove, using a gasket or decal remover softens them up making this a easy job, this type of gasket as been used for many years.

Just saw your post about the 5.5 head, you and the old girl are going to like it.