Thanks for all the welcomes! Jeff, I've actually got Mr. Bunn's book in front of me. "Dodge's Pilot-House Safety Cab pickups came close to being all-new trucks... The Pilot-House cab was higher, wider, longer, fully weatherproofed and provided excellent vision through its large, non-opening windshield." (p. 62-63, Dodge Pickups History and Restoration Guide).
Anyhow, terminology aside, thanks for the warm welcome, all (I think I'll just use B-series in the future ).
Nabbing the 4 units was kind of accidental. The blue '51 I bought at auction (plated it and drove it home), the yellow one's owner was moving and needed it gone (blew a head gasket a couple of years ago, not currently running), and the last two were a package deal from an area farmer. His father had bought the Dodge new and years later picked up the Fargo, which by then was already beaten up a bit. Both engines are in running condition, though.