I recently swapped the rear ends from a 1984 v6 firebird into my 1989 firebird they were both 10 bolt rears. But the v6 car had higher gears so what I'm wondering is will the speedometer drive gears swap also? I know my 89 has an electric speedo so before i go through the effort I wanted to see if it's been done.

 

they have online calculators that tell you what drive gear youll need for your rear end and tire size, if the calculator result ends up being the same driven gear as the one in the 1984 firebird then you should be all set as long as you have the same drive gear color as the 1984 car.