[Mike C]

'89 is officially when GM went 30 spline on the 10 bolt. In the front as well from '89-'91 but seems that they had a lot of 28's to use up so check the front to make sure.

I would not run the Spartan in the rear on the street and probably not in the front either. TruTracs in both ends would be how I would spend my money. I have a CJ-5 with Powertrax NoSlips in both ends and they are significantly more street friendly than the Spartan/LockRight style.

A Yukon/Eaton clutch type LSD in both ends would be a good choice as well. In my kids Jimmy we put a '79 Trans Am clutch posi in the front and running Gov-Lok rear in 8 lug SF 14 bolt.

I also agree that if you are considering buying upgraded axle shafts just convert to a SF 14 bolt and TruTrac or Yukon LSD for the street. I found 9.5" 14 bolt Yukon LSD for $389 on Amazon a year ago. Not sure what selling for now. The 33 spline rear shafts are absolutely massive on the SF 14 compared to the 30 spline 10 bolt axles.