741 Housing, 742 ring and pinion..... can it be done?
Well according to this, the outer pinion bearing and race/cup are the same between 741 and 489. It's just finding the larger bearing that will fit on a 489 shaft but fit the smaller race/cup. I don't think it can be done. The way yours was done 741 ring and pinion in a 489 case you would only need to find a race/cup that was thick enough to fit the larger hole.
Moparts Tech Archive
Rear Axle
Rear End Bearings & Seals Part Numbers
Rear End Bearings and Seals
By the way, these are National seal numbers, and BCA bearing numbers. Dennis
8 3/4" 3rd member bearings.
741 case
Differential 57-early 69: 25590/25520
Differential Late 69-74: LM104949/LM104912
Pinion inner: HM89446/HM89410
Pinion outer:M88048/M88010
Seal: 8515N
742 case
Differential : 25590/25520
Pinion inner: HM803149/HM803110
Pinion outer: HM89443/HM89410
Seal: 7216
489 case
Differential: LM104949/LM104912
Pinion inner: M804049/M804010
Pinion outer: M88048/M88010
Seal: 5126
Well according to this, the outer pinion bearing and race/cup are the same between 741 and 489. It's just finding the larger bearing that will fit on a 489 shaft but fit the smaller race/cup. I don't think it can be done. The way yours was done 741 ring and pinion in a 489 case you would only need to find a race/cup that was thick enough to fit the larger hole.
Moparts Tech Archive
Rear Axle
Rear End Bearings & Seals Part Numbers
Rear End Bearings and Seals
By the way, these are National seal numbers, and BCA bearing numbers. Dennis
8 3/4" 3rd member bearings.
741 case
Differential 57-early 69: 25590/25520
Differential Late 69-74: LM104949/LM104912
Pinion inner: HM89446/HM89410
Pinion outer:M88048/M88010
Seal: 8515N
742 case
Differential : 25590/25520
Pinion inner: HM803149/HM803110
Pinion outer: HM89443/HM89410
Seal: 7216
489 case
Differential: LM104949/LM104912
Pinion inner: M804049/M804010
Pinion outer: M88048/M88010
Seal: 5126