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Kind of an unusual question you have. I don't think that there is any "easy" way to do that. Especially since there are brushguards out there specifically made for your Explorer. The mounting points and bracketry are bound to be different between the 2 vehicles, plus the Nissan guard may not follow the Explorer's body lines very well--may look funny.
If you're bent on doing it this way, I'd suggest you get under the Nissan to see how the guard bolts up, and then get under your Explorer and see if you can do something similar. Either that, or weld up some custom mounts for the guard that fit your Explorer.