I will be replacing the stock differential on my '69 Mach 1 with a Detroit Locker. I am currently at 325 rwhp behind a C-6 and that rear wheel number will climb by about 40 hp once the heads and intake are ported and the new carb goes on. I will also be adding a 125 shot of nitrous. The car will see a drag strip about 6-10 times a year with about 4-5 runs per event. Do I need 31 spline axels with the locker, my level of power, and the kind of racing I plan on doing or can I get by with 28s?