rear end ratio
 

I would like to know the rear end gear ratio on 1991 firebird. thanks

depends, what all does it have (engine, transmission)

1991 was the change over year for the location of the SPID label. Early production has it in the center console glove box, late production will have it on the lockable storage compartment lid on the left hand side of the trunk area.

It will have the RPO codes for all installed parts and options. Axle ratio code will be in the Gxx series. That will tell you what ratio the car was built with.