it's on the top of the column, up under the dash... in exactly the same place that it's been on almost every rwd GM car and truck from the time they put the ignition switch in the column ('69 model year in passenger cars, '73 model year in pickups) until around the year 2000 or so.. the only exceptions i can think of are the 82 and newer F bodies, the Monza/Vega H bodies of the 70's, and the Corvette: all of which are cars that never had a column shift, so they put the neutral safety switch on the shifter in them, but they still had an interlock to prevent shifting out of park without turning the key on or turning the key off without shifting into park..
on cars with the neutral safety switch on the column that had a floor shift, they used the same linkage in the engine bay that would be used for a column shift to turn the outer collar on the columns to tell the switch and key cylinder what gear it was in and only allow it to crank in park or neutral and only allow the key to go back to "off" if the trans was in park.. this same switch also turns on the backup lights when the car is put in reverse..
i'm not sure how they did it on the fwd cars in the 80's, but i think it was similar... if the car came standard with a column shift, then it was mounted on the column and the floor shift cars had a cable going to the column to "tell" it what gear it was in and have all the safety interlocks in place..
some older rwd cars with manual transmissions had a linkage that went up from the reverse linkage arm to the column to activate the reverse lights and allow the key to only be turned "off" with the car in reverse, but the neutral safety switch was wired thru the clutch pedal so it would only crank if the clutch pedal was pushed in..
if your car starts with the shifter in any position other than "park" or "neutral", then someone propbably bypassed the neutral safety switch for whatever reason... if your reverse lights also don't work and you can shift it out of park with the key off, then the linkage from the transmission up to the column has probably been removed because that's, like, complicated and stuff..