The 8.8 rear in supers is surprisingly good. It's a nodular aluminum case, and has the large diameter ring gear. I've only seen them break when people hit the curb, or downshift from fifth to first gear, then only the rear cover breaks. This rear holds up to 640 lb/ft without problem, but never put on slicks with that power output and dumped the clutch at 5000rpm. The Tremec you'd probubly run will break first.
If you put in a different differential in the 8.8, you may have to grind .100" or so of the ends on the axles that stick into the diff. Otherwise, the bottom out on the cross shaft that spiders ride on since it's bigger now. That will not allow the retainer rings to seat where they should, the axles will come out 1/2" and gear
oil will be able to leak out the axle seals.
The only issue wuth SPF rearends is on the older ones, before they reinforced the forward mounts. The pass side forward diff mount would tear on the cars that make 500 lb/ft or more that have hard drivers.
The axles are quite sturdy, but the CV boots can and do tear. Really good ones are available though if you do need to replace them. On older cars they also can get the band unwrapped off the inner CV if thre rear torques over too far and lets it kiss the framrail. This was corrected a while back by SPF as they moved the diff about 3/8" to avoid this contact.