Just “eye ball” measuring various comparable points in each photo Utah posted above, it appears one bracket is a bit larger? It seems most noticeable in comparing the area just to the left of the red arrow shown in his photo, with the corresponding area on the other bracket?
Maybe actually measuring comparable points and comparing notes. would help?

The 1946 Chevron Master Parts Catalog, page 222, Group 4.648 does list separate parts for 3 and 4 speed brackets. The brackets for each fit model years from ‘36 through’46, GC and DP models.