Can you put 4.2 motor in 2001 excurcion?

No, you can't directly put a 4.2L engine into a 2001 Excursion. The 2001 Excursion was not designed for a 4.2L engine. It came with significantly larger engines (like the 5.4L V8 or the 6.8L V10). The engine mounts, transmission, wiring harness, and numerous other components are incompatible. A swap would require an extensive and incredibly complex rebuild, likely costing far more than the value of the vehicle. It's not a practical or feasible modification.