2001 2.7 motor into a 2003 2.7 car

[tholyoak]

You could swap the heads from the 2003 onto the 2001 and it would then work. To use the 2001 as is you would have to backdate the car to a 7.2 DME, not a smart thing to do.
There are lots of motors out there, my advice would be to sell the 2001 and buy the correct engine...well actually my advice would be to stick a 3.6 or 3.8 in there, it is very simple on a 2003.

-todd