If it's got the audible warning, it may be located in a "convenience center" which may also house the hazard flasher, door chime buzzer, etc. In the trucks it's over the gas pedal.
Not sure they'd use a relay, probably didn't need one since there would be very little load on the circuit. If the alarm for key in ignition/headlights on, I'd probably suspect something else.
I have the '88 Camaro service manual at home if you need me to check and see if I can find anything additional.