8 3/4 axels???
To answer the other questions
All of the posi units interchange, the one in my 741 case came from a 489 case housing.
You can use stock axles up to a 400 hp car with no problem. I like the green bearings , use them on a my race car and will probably use them on my street car (and hope I get to drive enough to wear them out!!).
Bob