Doh!!!!
I read that if you can get a socket on the lower bolts of the carrier then you have an 8” rear end.
It was not clear to this noob that the test meant actually being able to remove of the nut with a socket… which would obviously involve a ratchet and an extension.
The socket fits just fine on my 9”… but I’ll be using a box end to remove the nuts. 
.
Brian
Cylinder Index = 84
Current Experiment = `57 Tbird, Grand Rapids, Michigan