The Powertech 4.7 has never been used in the LX platform...or any other car, for that matter. It's strictly an SUV/truck engine.
You might be able to wedge one in there with enough fabrication, because the LX and the 4.7 have the 42RLE transmission in common. It almost certainly wouldn't fit under the hood with the stock intake. And the accessory drives are different, along with fuel, vacuum, heat and cooling lines, etc.
The biggest problem is the electronics. You'd need someone skilled with the CANBUS systems on both the 300 and the truck to try and get them to talk to each other, which will be very challenging.
You can swap in almost anything if you throw enough money at it, but this one is just not practical.