From what I have seen there are at least two areas on a Ford 9 inch that have different bearings...
Carrier bearings...I have seen at least three sizes...the biggest ones were to allow 31 spline axles to pass through and the smaller ones were for 28 spline axles.
On most older housings...metal was removed to allow for the bigger bearings...and with an 'N' housing the composition of the metal was better...'nodular' was the term of recognition.
Watch out for much older housings that have extra ribs but less alloying metals in the matrix...they will fracture and ruin your day.
Moving right along with the bearing differences...
Axle bearings at the brake hub...I have seen two different sizes...the older style and the newer, 'Torino' style...makes a difference which brakes you can bolt up...'Torino' style is larger and has a bigger bolt pattern.
On the pinion bearings...I have seen at least two different setups...and one that used spacers instead of a crush sleeve...the original ones (spacers) were called 'Daytona' pinion bearing supports...
I imagine...but do not know for sure...I don't have my parts catalogs with me...that the 'Daytona' bearings were larger and the pedestrian (is there such a thing with anything that Ford builds for truck use or performance..?) ones are smaller...
The aftermarket makes all sorts of stuff for 9 inch...you can't go wrong with it if you don't need a full-floater...
I used to love to build 9 inchers...they were the hot ticket for drag racing...
Can you show a pic of your housing and pinion support...and the part numbers...?
what exactly and where in the housing is the big vs small bearing?