.. 8 1/4 rear end ID ? ..

i just took a 8 1/4" rear end out from under my '66 cuda to replace it with a 8 3/4" i have .. the 8 1/4" unit has 4.10 gears with a SG .. i will be getting rid of it, but was wanting to know a little more about its original identification ..
it has 11.00" dia brake drums with a BPP ... any ideas regarding what it came out of ?? ..