Additionally, the 1981 Datsun 720 Ute is a much older vehicle than the 1989 Nissan Navara Ute, and there may be differences in the electrical systems, fuel systems, and other components that could make the engine swap challenging.
It is always recommended to consult with a professional mechanic or automotive specialist before attempting a major engine swap to ensure that it is feasible and can be done safely and effectively.