Argosy Hartwell door latch on ebay
Currently on ebay is a Hartwell entry door latch assembly that was used on the early Argosy motorhomes. I know my 74 Argosy mh has this latch assembly and I'm guessing the latch works on 74-76 Argosy motorhomes and possibly trailers as well.
Hartwell entry door latch
These latches show up very infrequently. The price might be a little high but if you need a replacement latch this might work for you.
No financial interest, just trying to pass on what I have found.
Air forums # 1674
1974 20' Argosy Motor Home
1974 31' Excella trailer (parting out, as of 4/1/2015 I have wheels, brake drums, windows & holding tanks left to sell)