I had another look at the CMP truck parts manuals (will post a picture later), and it is clear to me that the Chevrolet truck axle had an outer axle seal as pictured above. The Ford truck axle had an inner axle seal, just behind the differential bearing - so no need for a seal at the outer bearing.
Proving again that the Ford design was superior over the Chevrolet
(Carriers are a different matter, I'm talking about the trucks here.)
H.