[ford38v8]

The sky is not falling, all parts will remain in the top tank until flushed out, none small enough to enter the tubes, which is the only way to the bottom tank. Consider if it's time to remove and give your radiator a professional clean-out, or to do a driveway flush-out. Work smart to keep your engine compartment clean while you redirect the top hoses with a sock to catch your parts and other debris while you backflush. Another option worthy of consideration would be to take a cooler full of beer to the front porch and have a friend over to help you drink it.