8-1/4" rear end questions?
The vast majority of automotive axles use C-clips to retain the axle and the c-clip or the end of the axle where the c-clips sits seldom fails. The issue with a c-clip design is if the axle it self breaks outboard of the splines and c-clip which then means there is nothing retaining the end of the axle and wheel and they will come off. If that is a concern there are kits availble that elminate the c-clip and retain the axle out at the end so the wheel won't come off.
The weak point in the 7.25 axle was the carrier and specifically the spider gears. The few 7.25 axles that were delivered with sure grip differentials were substantially stronger.
My understanding of the 8.25's weak point is the housing will deflect resulting in bearing failure or allowing the gears to seperate resulting in gear failure. This can be improved substaintilly with a cast cover that has jack screws that support and stabilize the carrier bearing caps.
I have seen articles that 8.25's with better axles, a strong diff, careful assembly and one of the support covers will survive behind 600 hp small blocks.