Originally Posted by 1942ChevyPfost
. . . .
This pipe plug is the fill plug on the top of the steering box correct?

1942?

Yes, it is a/the pipe plug.

Fill to just below below the base of the hole.
Drive/steer the truck.
Re-check the level and fill to just below the pipe hole.

http://chevy.oldcarmanualproject.com/shop/1942/42csm0011.htm