Identifying rearend

sorry for intruding just could use some info.
I thought all 8.75 5 on 4" rear ends were sure grips ?
do the number codes on the outside tell what gear ratio is inside? or do you have to open it up? I have one in my 65 cuda pretty sure it was a swap in but not sure.
And I have one in my 67 cuda that i pulled out of a 70 dart 20 years ago?