Yes, it is possible. All things are possible. I have the same ute (2004 Model) and mine has all the wiring for power windows AND Central Locking already in place. You just need to get the parts. You can start with asking your local Toyota Dealership, then move on to searching online for Aftermarket suppliers. I've actually bought (7 or 8 years ago) the Central locking kit for mine, Just gotta get around to fitting it ... It's on my "to-do" list, but the missus has higher priorities than I do.
Take Care and "Have Fun With It"!!!