Good solid trucks and capable of towing 14k when set up right, from a suspension and chassis standpoint.
The V10 will get er done and will last a long time without complaining, but don't expect it to pull grades, or even flat road like a diesel. If you're pulling a say 4-6% grade, expect to drop to 2nd gear wound up to maintain speed.
I've never towed with them at low altitude, only high altitude, so the effect was magnified by the 20-30% less power compared to the OE ratings, but you'll still be working it at 100% output on any hills. Expect 6-8 mpg.
All that said, they are one of the best gasser combos out there, still, IMO. And 05 is past the spark plug spitting era and has the 5 speed torq shift. In my experience it doesn't give up much if anything to the 6.2s in the '11-16 models. Have towed a bunch with both.
Personally though I wouldn't want to tow 14k regularly with any gasser truck, new or old, if a better option was in the cards.
However, local trips or at least east of the Rockies, it'll work. Head to the mountains and you'll not be real happy.