Before this big, bad pickup arrived, manufacturers largely used upgraded versions of their light-duty trucks to handle heavy-duty work. The 1999 Super Duty was a separate model line with its own style and hardware underneath.
You can run a conventional oil 5K miles but you should be able to run a synthetic oil 7500 to 10000 miles. Royal Purple API-licensed synthetic engine oils allow motorists to travel as many as 12,000 miles as the recommended oil change interval.
Some synthetics however will only allow a 7,500 or 8,000 mile OCI. The OCI assumes that you have a high quality fully synthetic oil in your car, which the factory oil (and that which the dealers will change your oil with) is not. My oil change cycle is 1,500, 6,000, 10,000, and then every 5,000 miles. I balance, rotate, and inspect my tires every 5,000 miles.