if the dino worked good for 150k i would stay with that. tested and proven to work for you for that long.
bob the oil guy is the best oil forum ever. http://www.bobistheoilguy.com/
research the different properties and find out what oil is best for your motor.
some dino oils out perform synthetic oils and vise verse
keep changing the oil in 3k miles so the sludge doesnt build up and most oils will get the job done.
remember to let your truck warm up when its cold outside too. the oil works best at a certain temp.