Don't know why you would want to remove the heads. We stored Cummins and Detroit Diesel engines in our shop warehouse on pallets and did nothing special to them. Some we had overhauled for storage, some were used. Whenever we tore a used one apart to overhaul before putting it in service the bearing surfaces, etc, had just as much oil coating as if they'd just been shut down rather than sitting for a year or two. You might want to pull the glow plugs and shoot a small squirt of oil into each cylinder.