My initial impression was that you wanted to have a permantly installed load bank for regular standby diesel testing, which is typically the case for installations where the grid feeds the loads while an emergency stanby diesel is used for critical loads only when the grid is down. As it may take years in some cases for grid to go down, some places do install a permanet load bank for regular periodic generator testing.
But if that is not the case at your facility, why would you need need to purchase a load bank? Why not rent one if you need it for a week or similar to test governor and AVR reponse or so? Sounds that you may be a PM with no electrical background and if so perhaps getting some electrical help would be practical at this stage...