To fit the higher ratio (smaller number) gears, the flange on the carrier is moved over a bit. This gives room for the larger diameter pinion gear required. The ring gears are also machined specifically for the application, so they do not interchange. I suppose you could make a spacer to use the lower gears with the carrier, but you would have to know the exact thickness required and the bolts could be a problem. For the precise machining required, better to purchase the required carrier.