I would recommend going with a diesel. I have a Powerstroke F250 and a 6 speed. It'll pull anything you want just about as fast as you want. I know the Duramax (for all you Chevy guys) is a great engine, too. The good thing about the Powerstroke is it's easy and relatively cheap to add LOTS of HP and Torque. My truck runs about 325 hp and 600 ft-lbs and I've only chipped it!!! (about $400)
Much more to come!! I drove a Chevy Gasser for years and liked it until I got the Ford.
With all the financing specials, etc that have been going on, the slightly used market is flooded with trucks. I think you could probably get a pretty good deal on a truck that's only a few years old.
Just my 2 cents..........
Jason