9 sec combo with 8.75...

It's a function of weight at that speed IMO. If the car is heavy, you're simply putting off the inevitable breakage by using an 8 3/4 axle. I guess my question would be if you're building a 9 second car, why would you not use the strongest rear available? You can run pro gears that are race only and help absorb the shock, twist housing tubes, break the caps, shear the pinion, possibly hurt the transmission.. For what? A few years and some hundreds of bucks? You're spending coin on the suspension... Spend it on the rear axle too and be done with it. JMO of course.