Have reseached this front loader attachment thing some more.
Found the sales brochure for the Ford Industrial Step-On loader you previously posted.
Believe is the same as the Ford extra heavy duty series 703 loader.
Also the brackets shown in your last post are hydraulic pump attachment brackets for thr FORD 68 standard loader, Ford heavy duty loader and Ford 79 standard loader and not the loader frame front attachment bracket.
The graphic appears to be is taken from the Supplement No 3, master parts books.
This parts book show two 1" bolts in Figure 4 for attaching loader fram to bracket.
However, the bracket shown in figure 6 does not appear to interface with an N series, maybe a 600 series.
I agree with you on the location of the loader frame front support for all of the Ford Dearborn front end loaders where the attachment is to a replacement king pin or to the axle center support weldment.
It appears that on the Ford 19-8A or 19-22 the original king pin is replaced with another king pin with a steel plate welded to the king pin. The king pin plate has two holes that interface with a steel plate welded to the loader frame.
Maybe other Ford loaders manufactured for N series has this type of front attachment design.
However , found the parts manual for the Ford 19-7 ,where front attachment appears to interface with four bolt holes on the axle center support engine pan holes. There are two bracket plates, one each side of the center support.
A free body diagram of the loader support frame indicates a force is applied at the axle hole ~ 2800# ,based on 1000# payload and bucket weight at lowest position. The greatest load is applied to the from axle in the lowest bucket position.
Need to firm up some geometry to better converge on this applied axle force at the center.
I know there is low probability for castropic failure of the cast axle part, but it would not get an FAA certification for flight.
It's a tractor.
Still do not understand the rotation feature front axle.
Seems like for a front end loader it would more desirable for the front axle to be fixed.
All the NH & JD utility tractor brochures show a front end loader on the cover. This still must be the hot ticker demand for utility tractors.