While both vehicles are Ford products and share some platform similarities, there are differences in engine bay design, mounting points, and ancillary components that prevent a direct swap. Even if the engine itself *might* physically fit, the associated wiring harnesses, computer modules, and exhaust systems would almost certainly be incompatible.
You'd need extensive fabrication and custom engineering to make such a swap work, and the cost and effort would far outweigh the benefits. It's far simpler and more cost-effective to repair or replace the existing engine in the Navigator or choose a compatible replacement engine.
