They do/did make Nissan motors that were non-interferance designs so that should the timing belt let go it wouldn't destroy the motor.

No clue on your Trooper, though, I would call an
Isuzu dealer and ask them if your motor is a non-interferance motor or not...we may be technically inclined here, but it's usually more with regards to the Xterra.

The other route to go would be to find an Isuzu/Trooper forum as well