Your rear end was designed for a 235 six cylinder not a V8. That is why GM replaced the whole rear end with the Spicer series of modified Dana rears in 1965. GM did offer a rear end designed for V8's and a straight eight Olds with the strongest ones made from 1957 through 1964 and where under all of GM's cars except the Chevy.
even at 500hp/tq, I think you'd either need what Dave mentions, or just go aftermarket like Currie, Drivetrain Specialists or Mark Williams or something. besides the beefed up gears/posi-unit, the axle tubes will probably need to be welded to the center section I think. My '66 10-bolt model and many GM others only had small pins keeping them pressed in place.
Too much torque/traction can cause the tube to rotate which is sooo not good.