8 1/4 rear end

I was reading the new Mopar Muscle street shoot out, and read about a guy running 10.66 NOS and 11.s on the motor in a 340 4 speed 4:10 geared Duster. He says he runs a spool and does occasional street duty. Most people here say the 8 1/4 isn't good for much horsepower. So, what breaks? Is the spool why his rear lasts? Is he a member of this board?