is it a 8 or 9 inch? what are the factory gears for it? its and auto

 

i forgot to add it was a V8.

 

Which V8? S and R codes (not that it came from an R code, but still) came with 9" rears. All others came with 8" rears.

Stock gearing is likely 3.00:1 or 2.79:1. The door tag, if original, will have axle info on it. The axle itself may also have an ID tag on it, although they're commonly missing after 40 years.