To get an "accurate" temp reading, you will need the temp sender unit from the donor cars engine.
Toyota have always played with these little jiggers. The First Camry's exported to UAE in the desert, had the same sender as the Aussie Camry's. The Locals over there were concerned that the guage wasn't reading high enough for the warmer climate! Toyota's fix --- change the sender unit, so that the needle sat higher!