Building rear differential

[grousehunter 61]

I am rebuilding the rear differential in my 71 short box 4x4. I bought the center housing from Summit racing and am using my original ring and pinion. the housing they sent is a Yukon. I am having nothing but problems. using the spacers that came with the kit on the pinion I can not get the ring to match up with the pinion. If I put all the spacers on the center carrier on the left side I can get it close, but the carrier then hits the right side of the differential housing hard enough to lock it up, if I put the spacer on the right side it pushed the ring gear away from the pinion to the point that I have about 30 thousands back lash. The kit is YGA26052 that summit says is for that truck. I used all the spacers on the pinion that came in the kit but still no contact or no correct contact with the ring. Of course everything is closed for the weekend. any ideas on what I am doing wrong ?? this is a one owner truck and I am that owner, bought it new july 20 1971 so I know nothing has been changed.