A friend of mine purchased a 3rd gen 9-1/4" rear and I'm almost certain he told me that it was a bit longer than the 2nd gen rear he had. In addition, the spring perches on the 3rd gen rear did not line up in the location of the 2nd gen rear setup. At a minimum, new springs perches would have to be installed on the rear to make it fit correctly. Since my friend's truck is 2WD, not sure about how the front axle would fit, however, if the rear is a bit different, I'd expect the front to be slightly different as well.