IFFFFFFFFF--it hasn't been run a lot lately-it could just be from condensation formed in the exhaust system over numerous short running periods-like starting backing out of garage. Starting and loading on and off trailer, etc,etc---------it may all dry out and go away with a little running-
but do keep a look out at the oil condition on dipstick and possibly remove valve cover to see if moisture cooletting inside on the alum.

You also might want to loosen rad cap to see if getting any bubbles or pressure build up

also there is a bottle of liquid stuff and an tool that you can vent rad thru that will chahge color if exhaust is present.
as for oil--this engine has mushroom tappets and being larger diameter than most lifters, the oil used isn't as big a problem as on other engines plus the upper engine was fed separatedly from cam bearing location 2 and 4 and drain back worked------