Hi nathan. They look a little generic to me. All the rear fittings I have seen including a few that were documented factory fittings had 3 sides to them. 2 side walls and a top. No time to b.s. right now, but see what others come up with.
Definitely for floats. I've seen them, like this, on Cubs, T-crafts, SuperCubs and Champs. I'm wondering if it's a generic weld on fitting from F.Atlee Dodge or if they're Make/Model specific.
They resemble the Atlee Dodge fitting. Look inside the fuselage and see if there is a square plate about 4" x 4" welded to the fittings and fuselage tube. I just put a set on my Chief and was not quite happy with the fit, but they are very well made. Dodge will probably e mail a drawing if you ask.
I have some detailed photos of EDO float fittings (1320's) and they do not look like yours in the picture at all. I can eimal them to you if you would like. mastercfi@yahoo.com
The fittings can be either bolted on or welded fast
Upstate NY CFI Tailwheelm Instrument - Land and Sea (Float Champ)