Make sure you have a good oil filter. Start up clatter can be from an oil filter with a weak anti drain back valve. The Motorcraft FL 820S includes a red silicon anti drain back valve to prevent this. If you have not changed the oil filter yet or have been using something with a weak anti drain back valve, try changing the filter before you do anything else.
The 95's had a problem with the cam chain tensioners leaking down. It is possible for a 98 as well, but not as likely since they were redesigned long before then.
