Mopar 9 1/4 narrowing

You'll lose some strength going from the 30 to 29 spline axles unless someone is making 30 or 35 spline side gears or spools for these axles. I've always seen a lot more other parts let go before an axle snaps, a Ratech high strength crush sleeve or solid crush sleeve eliminator would be a good plan if using any Chry-Co crush sleeve rear axle.