Antifreeze puddle on time change cover

Are you uncertain as to where the coolant is coming from? Is it traveling to the timing cover, or is it originating there? A 1990 5.0L could very well have a leak from the housing itself. Or it could be from a worn out hose not sealing entirely. Check clamps and even pull the hoses off, looking for pin-holes or cracks. When you disturb them, that's when they especially start leaking as they are aged.