The intent of having equal length axle shafts is to make having spares easier. The result of building a 9” to have equal length axle shafts is a pinion gear offset about 2.2”.
My question is…. Is having that much offset (about an inch more than a 8.75) a bad thing? If so, why?
Well to me, a pair of axles cost the same regardless, so I just ordered a second set and called it a day. The odds of me breaking a dana 60 35 spline axle at my power level is slim. Your mileage may vary