I have 275/70/17 Firestone Destination AT's, and they're LT tires. I thought all the Destination AT's were LT's.

Great tires BTW. They handle snow very well, great wet road traction, and are ultra quiet on the road. I noticed a huge difference in handling (not as loose, less sidewall give), and especially noise, over the General Americraps (P rated) the truck came with from the factory. The Generals did a lot of humming at 80 kmh. I have pics in my gallery. The pic in my sig is with the factory Generals, 255/70/17's.
They seem to be wearing well. I have about 20,000 km's on them now, but they do need to be rebalanced. I'm getting that done ASAP. I took it in yesterday but the tire dude striped my key for the lock. I'll be getting rid of the locks and replacing them with regular lug nuts. Locks and keys have no business being on a truck, especially a truck that has a torque rating of 150 foot lb's.

 

Agreed that the p series in general is within the capacity. P series have their pros and cons, just like anything else. Pros for the P series are price and they are speed rated. Cons are they are at their limit for an F150, otherwise there would be no reason to run them at max pressure, Also their sidewalls leave a lot to be desired when it comes to things like cornering. I have LT LR C tires on mine. At 40 psi (max 50), they can handle anything the f150 is rated for and still have a safety margin not available with p series. Also they handle cornering far better than the p series on a vehicle with a high CG. Whether loaded or unloaded, they are far superior for that. The main reason I run LT tires.