I just purchased this truck used with 100,000 miles on it. Since then I have discovered two things you need to watch out for on this truck:
1. The 4.7L V8 is an interference engine. The service interval is 90,000 miles. If you allow the timing belt to break, it will destroy the valves. Be sure you take this maintenance item into consideration. Have the water pump and idler/tensioner pulleys replaced at the same time you have the belt serviced. Expect to pay $500-$900 for parts and labor.
2. Toyota has issued several recalls for excessive frame corrosion. Check to be sure the frame is not excessively corroded and that the recall items are taken care of.