I've got 203,xxx on my '02 4.0 and the thing starts and runs like its brand new. I have every maintenance record for every little thing done to it. I am the second owner and have put 50,000 miles on it in three years. Damn good trucks, these 4.0 SOHC Rangers are.
a guy I work with has an '03 Mazda B4000 (same engine) with 350k on it. He is a traveling salesman, so they are all highway miles, but he is just now starting to have a little transmission trouble. He's never had any big engine trouble.