Mine is an 01, so 99% the same truck. I also put an AFE dry air filter in the stock housing and that's it for drivetrain upgrades.
Definitely this. It's an interesting engine... Just give it more throttle, let it rev, and it'll pull anything within reason. Being an older chassis, 10k is about all I trust it for with a frame mounted hitch.
OH SHIT! Something I remembered: if it has the factory Ford hitch, pull it off and cut it up for scrap steel. These came with a frame mounted hitch that was rated for...
5000 pounds.
That's it.
The chassis itself with the V10 is rated to tow 10k with 3.73s and I think 12.5k with 4.30s. Fifth wheel is higher of course. It scares me to think about how many people are pulling 10k loads on that factory 5k hitch. The stickers get old and fall off, or covered with undercoat, and most people just assume it matches the truck's capacity.