They are entirely different, end to end. The carriers won't fit in either. The 10.5 FF axle tubes won't accept the SF bearings, the 9.5 carrier won't accept the FF axles, and the pinions are different. There are also differences from year to year, and not all "G80" L/S or Lockers are the same, even in the same axle designation. "G80" is only the RPO code for "Locking Axle", and the same code spans decades, despite the hardware actually used for that year model. RPO codes are only a general indicator of the presence of an equipment feature. For example, L65 is the RPO for the HD 6.5L Turbo Diesel, while L56 is the code for the LD 6.5L Turbo Diesel. The same code is used from 1992 to 2003, with no distinction for technology or mechanical upgrades over the years.