Just changed the fluid on my 91.5 today there are numbers under the diff cover on the housing at the bottom upside down.

 

The 92's had 3.54 and 4.10's available in both auto's and sticks. The 3.07 ratio in a intercooled truck from the factory is very rare. The common 3.07's were in the early non cooled trucks with a 727 3 speed auto.

 

yea i have 3.54 in my auto. i want to find a 3.07 though if anyone could help me out there

 

just pull the cover, throw a jack under it so you can turn the tires. mark the ring and pinion with a marker and count the teeth one one full turn till you see your mark again. divide the numbers together itll give you your ratio. thats the best way IMO it gives you it for sure even if someone changed it before or something. and that way it gives you an excuse to drain and fill your fluid which most people lack on