Backlash spec on the 14 bolt is 3-12 thou, with 5-8 thou being best. I'm trying to stay on the tight side of the range to help a bit with strength - but only if the pattern supports it.
Edit: Jeeze, I can't believe I typed that. Help a bit with strength - ON A 14 FREAKIN' BOLT!
When you think about the horsepower and tire size you run compared to anything factory it makes sense. GM would spec a much larger axle for that application.