what is the difference in a 07 mercury grand marquis 4.6 L engine and a 04 F150 4.6 and can they be switched

The 4.6 Liter V8 in an '07 Grand Marquis and an '04 F-150 are fundamentally identical. They're part of FoMoCo's "Triton" SOHC V6/V8/V10 engine family that was introduced in the 1990 Lincoln Town Car and subsequently replaced the old OHV small and big block V8s across the board at FoMoCo. However, even if the engine is the same, the workload it is expected to shoulder is quite different in a semi-luxury sedan like the Grand Marquis on the one hand and a light truck like the F-150 on the other hand. The '07 Merc's standard 4.6 makes 224 horsepower at 4,800 rpm and 272 lb-ft of torque at 4,000 rpm whereas the equivalent data for the '04 F-150 are 231 horsepower at 4,750 and 293 lb-ft at 3,500. The torque curve of a truck engine is flatter of necessity than that of a car engine. If the same engine is used in both applications, the electronic controls must be tuned accordingly. I doubt an engine swap like the one you envision can be conducted without more or less extensive modifications of the recipient vehicle's engine management system. In addition, the automatic transmissions in both vehicles are digitally tuned to the respective engines they're connected with, so that would require computer modifications, too. Finally, there's the question of different engine mounts in both vehicles, a mere mechanical but not a negligible problem. In summation, I believe an engine swap is not impossible but it would require considerable expertise in electronics if the engine is supposed to run smoothly in the recipient vehicle. As usual in today's automobiles, the omnipresent computer systems are the home mechanic's nightmare.