89-91 10 bolts are 30 spline front and rear on 4x4s. And you can drop a 8.6 carrier in your 8.5 housing with the conversion bearings and use your 8.5 ring and pinion. 8.6 are 30 spline and are in 88 up 1/2 ton trucks. Then use 12 bolt axles which are 30 spline. You may need to clearance the ends...