Howdy! Me being quite young and not as well versed in all things Thirdgen, I was wondering where would the Y84 code would be located?

 

Inside the center console.

 

Right:

In the early years of these cars, RPOs weren't required to be posted on the car at all; and only were there even to the limited extent that they were, as a matter of convenience in the factory.

In later years, regulations began to require uniform labeling of options in ALL cars for service purposes. Thus, the SPID sticker as we know it, was invented.

The change was in the late 80s; 87ish, though I can't be positive of the exact year any more.

Before that, ... coming across the list of RPOs for any given car was mostly a matter of luck. On the console lid for example, a part that isn't particularly securely attached to the car at all and often was replaced due to cosmetic damage.

 

The SPID sticker started appearing in 1984 on the ThirdGens while the data plate under the hood was still used until 1985. So some ThirdGens will have both. However, it has been said that the Y84 RPO (Special T/A for early ThirdGens) did not appear on the data plate. The data plate did not contain all RPO codes.