One problem related to rear suspension leaf spring leaf has been reported for the 2000 Ford F-350. The most recently reported issues are listed below.
Leaf springs broke while hauling loads. Pulling a 16 feet trailer with one small Mini pony spring broke, causes swaying in December 2006. Pulling 28 feet trailer on interstate in January 2006 had same thing happen. Now the 3rd event using 30 feet horse trailer taking 6 horses to farrier had same problem. Could cause serious accident by forcing vehicle off road while towing.