I was recently faced with the same situation and changed out the whole rear axle assembly and got new upgraded brakes, diff, etc....
The rear axle assembly from a 1999 Chevrolet 3/4 Ton (2500) pickup fits perfectly - the backing plate to backing plate measurements were the same ! You only have to move the spring perches. As a bonus, the original driveshaft and u-joints also connected to the differential with no modifications. (U-joints for a 99 Chevy 3/4 ton with outside keepers)
My original driveshaft was approx 2" too long, but instead of cutting the driveshaft and having it welded and rebalanced, I cut the male (1") and female part (2") of the spline where it goes into the carrier bearing...and was back in business.
Works great and now I have no problems finding brake parts for my 1 ton Chevy. The new gear ratio is approx 3.77.
