I'd say it is probably designed for 300 HP max. But that would be a guess. I don't believe Ford ever figured on 500 HP being applied to an 8.8, but again, that's an assumption on my part. I've only seen one 9 inch with a bent tube and like you it was a take-out from a wrecking yard and probably damaged on removal or when "they" tossed it aside for storage.

I'd think a full circle weld done properly around the tube to cast housing would just about make the rear end bullet proof. But again, for how much horsepower? I'd still think 500 HP would be the limit. I'm not sure the stock splines can handle much more than that.