After reading the interchangeability sticky I am left with these conflicting pieces of information. Please confirm the correct information:
1993-1999 and 2000+. You CANNOT under any circumstances bolt a 2000+ engine into a 99 or older body or vice-versa. It simply does not work. Too many differences, too many sensors changed and the holes to mount them. Many people have tried, and gone through all of the work to bolt it in and realize that 1) some things don't bolt up correctly, 2) the wiring won't connect and 3) it won't run.
1993-1999 and 2000+. You CAN bolt a 2000+ POWERTRAIN UNIT into a 99 or older body or vice-versa. A 1998 and 1999 Seville will take a 2000+ unit from a Seville or Deville. You will need to repin connector C101. A 1996 to 1997 Seville, 1996 to 1999 Deville and a 1996 to 1999 Eldo will except a POWERTRAIN UNIT from a 2000+ Eldo. This is 100% functional and it will not have any DTC when done. Some of the other modules may need to be setup to match the VIN or you will need the VIN changed in the PCM to match the car.
POWERTRAIN UNIT: This is the complete unit including the Engine, Transmission, PCM, Harness. You may want to change the Cradle also.
Example: Just wheel the complete POWERTRAIN UNIT out of a 2005 Deville and under a 1998 Seville