Engine looks fine inside the lifter galley. The coolant passages are typical for an engine that sits for years with old or no coolant. Unless you want to pull the engine the best you can do is try and flush as much as you can with a garden hose. They do sell chemicals that supposedly help clean out the coolant system but it would take a few times and you would have to keep flushing out the system to remove all the residue. a good radiator shop could check and flush out the radiator and even take the tanks off and rod the core. Remember never to fill the system with tap water and only use distilled water and the proper antifreeze ratio.
