Not one to disagree, but there is not a snowmans chance in you know where, that by merely going to some hardened aftermarket axles it will solve the problem. That 9 inch will grenade the first time out of the box. 35 spline, 1 1/2 inch dia. 1/2 inch dia. wheel studs instead of 7/16. Nodular case and, not to repeat myself, but a back braced tube. Look at Currie, Dutchman Motorsport, Strange, Morrison and Mark Williams.
If he is running 800 at the rear wheels, with 750 lb/ft of torque, you have to have the best money can buy, or close to it.
http://www.markwilliams.com/technical/faq.html
Ron