You just need to swap your existing 4GM bracket to the 04+ horns. You can easily get these horns from a junkyard or part-out as this is not a highly sort after park.
Once you swap them, you may need to bend the brackets a little just to stay clear of the AC Condenser.
The ground plug is same for both so no need to do anything else.
The Anti-Theft on 4th generations has a Relay to disable the ignition if activated (relay located on the passenger side of the engine bay near right strut, look for “Anti-Theft/Start” on the relay box cover). When tripped it will ground power to the Inhibitor Relay that controls the starter solenoid.
THEFT-DETERRENT SYSTEM
To cancel the system and prevent accidental activation, perform any one of the following:
Using the key, unlock either the driver’s or passenger’s door.
Using the multi-remote control system, if installed, unlock doors.
Turn the ignition to the ACC or ON position.
Using the key, unlock the trunk lid. The system is only temporarily canceled while the trunk lid is open. After the trunk lid is closed, the system is reset.
To set the system, remove the key from the ignition, and close the doors, trunk, and hood. Then lock all doors either manually using individual door lock buttons, or activate the power lock system with either the key or the multi remote control system.
