I’m looking for a little direction on rebuilding the axle on my 72 Skylark. It currently has 28 spline shafts, look to be original, and in good shape; just pulled, inspected and measured them this afternoon. Open differential, 3.42 gears. I’m in the process of building up a Buick 350 for the car with the new TA heads, forged pistons and rods, TA 310 camshaft. Projecting power in the 400+ hp range, and torque in the 425 to 450 foot pounds. My question is whether this power/torque level needs 30 spline axles. I’m planning to replace the open diff with a TrueTrac unit and keep the 3.42 gears. This is a manual transmission car, if that makes any difference. The 3 speed Saginaw is coming out in favor of a Tremec TKO 500 when the new engine goes in. Planning to use this car mostly on the street with some occasional road course, autocross and possibly one or two trips down the drag strip.