If you upgrade it with a 30 spline Eaton Posi, 30 spline Moser axles and set the gears up with the correct contact pattern and bearing preload it shold be fine. If traction is good then you might want to weld the axle tubes. How to weld axle tubes on GM 8.5" 10-bolt - NastyZ28.com
This is the correct way to weld the tubes. Welding them with a MIG with steel wire will not work.
I've built several 8.5 rear ends like this and they have held up behind some 500+ cubic inch big blocks and are still working today.