Oh, don't get to worried, these cars being newer (OBD2), you won't have to change much. The ecm will pretty much control the engine independently, and the engine harness will plug right in.
Requirements for custom wiring generally come in on things that must communicate inside the car. Signals to the instrument cluster, alarm/security, etc... Usually not to hard, just comes down to locating the wire/pin on each cars schematic.
This is the area you see a lot of "unfinished" swaps, car runs and drives, but has no speedo, or the tach doesn't work, or the a/c doesn't work. You may have to make custom a/c hoses.