Start swapping....
Take out #1 and #2 spark plugs, swap them. If the misfire goes to #2 cylinder, you have a fouled or failed spark plug. If not, swap the plug wires (#1 and #2)-don't forget to swap them on the distributor cap as well. If your miss went to #2, you have a "bad" high tension lead (plug wire). If not, you've likely got a problem with the distributor cap or the distributor itself-but more likely the cap.
These engines are real sensitive on ignition components. Always use Motorcraft when you can and replace every 25,000 miles. For some reason they're kind of hard on ignition components or at least that's always been my experience with them.