I have a 2002 Ford F-150 4.2, and i was wondering if it would b possible to swap engines to a chevrolet 454 or to a ford 427.

 

With enough $$$ and capability in fabrication and conquering hardware/software issues, yes. Cost-effective? No. By far the best way to get where you want to go is to trade your truck in for something with a base engine that either has enough power out of the box, or has manufacturer/aftermarket support for a build-up.