I just got a Bargman 300 from a place called rvproshops. I used it to replace the original Hartwell on my '74 Argosy motorhome. The replacement wasn't simple, but I'm highly pleased with the result. The original was pretty much worn out, and it lacked the retainer bolts that the Bargman has. My door was apparently drilled and machined for some other model and/or brand of lock, too, since there are holes and slots that weren't used for the Hartwell and didn't match up with the Bargman.
Does anyone know when Airstream/Argosy started using the Bargman lock on motorhomes? One friend has a '78 Argosy that came with the Bargman, but another friend has a '79 Airstream that apparently didn't - his was obviously modified for the Bargman at some point.