It's a 1950 4100, but there have obviously been a lot of swaps along the way, so I don't think the year and model of the truck actually are any help in identifying the rear axle. Since I posted this, I've gotten some feedback from one vendor that seemed to know what he was talking about, indicating it came from a '73 - '75 International. His statment that it has a Powr-lok with 4.10 gears is consistent with what I see by spinning the wheels, counting driveshaft revolutions.
