On a bone stock front 60 (4.10s, 35 spline inners, 30 spline outers) I'd say 38s are going to be about the max and you can definately still break at that point. For a rear 60 (30 splines, 4.10s) I would say 37s. 14 bolt you can definately run 44s in stock trim. On gearing, the 60s can run up to 7.17s and for the 14 bolt, 5.13s are readily available but they are just coming out with 5.38s for them. If you are still running an "R" motor, I'd be looking more at the 60s if you drive on the street much. Only downside is the $350 for 35 spline rear shafts and the cost to bore the spindles too. If you know where to find them, you can get front 35 spline outers for $55 a piece and replacement Spicer joints for about $40.
