Who knows what about early 8-3/4s?

The 657 case is actually the precursor to the 741 case, and if it is indeed a 4:10 gear in that case, that would certainly be an anomaly. Which would lead me to believe the above comments that the housing, axles and center section came from a truck, tractor or some other industrial application. No factory 741 case was ever offered with a 4:10 for a vehicle destined for the road, and I’m actually surprised that it was even available at all.