Sounds like you are in the market for a either an F-150 or a Silverado 1500, both should suit your towing needs. I am a Ford guy, almost always have had Fords, and have had great luck with them. I currently have a '07 F-150 with almost 270,000 miles on it. I bought the truck used from a Ford dealer in June '11 with 51,XXX miles. I have the 5.4 in my truck, and it's been a great engine, it still gets good mileage, runs quiet, no issues. I have replaced the radiator, alternator, transmission, front wheel bearings several times, and a cam when I went too long between oil changes. With that being said, the 5.4 needs to be maintained religiously. They do have some issues with cam phasers acting up, and that can be a costly job. Knock on wood, I haven't had that issue.
The 4.6 V8 in these trucks don't quite have the same issues, as the 5.4, so that might be something to look at. The V6 trucks are a bit gutless in these trucks, and I would steer clear of them, especially if you want to do towing.
I think either truck will do well for you, just try, of course, to try and find one that was well cared for.