Removing intake manifold without getting coolant in engine

After draining the usual way, take out one or both - front or rear, exhaust manifold bolts, on both heads, to lower coolant level below port height.
As an alternative, a lower timing cover bolt could be removed, but that may cause an unwanted gskt/RTV leak.

If you're removing manifold to remove/replace lifter, on many stock heads, lifters can be removed/changed without removing intake.
Remove rocker shafts, may have to loosen one manifold bolt that protrudes, and using magnet or a welding rod tool, to pull lifters thru the opening in the head.
Cheers