Re: Help Needed!!!
33's would not be a "little" larger, they would be way larger and would require substantial suspension modification and gear changes. Don't go overboard on tire sizes, "biggest" is not necessarily the best. I ran 305's on a 4wd Diesel Excursion with no modifications, except for stiffer stock height front springs to prevent bottoming, and they worked great. If you go too big, you will need to address the issues mentioned by Chipset and Cat, and the results are not usually worth the expense.
As mentioned earlier, I will be in San Diego today and will check on my daughter's boyfriend's truck to see what size tires he's running. He has a 150, with larger tires, and it handles and runs great. But, he has big bucks in suspension modifications, mods which cost much more (thousands more!) than the initial cost for tires and wheels. Be prepared to take a big hit in gas mileage.
Where do you live, what type driving do you do, and what do you use the truck for?