The thing here is that the money spent on a 7.5 to "beef it up" is likely to be exactly the same amount or close to it that it'll take to beef up an 8.8, and in the end you'll have a MUCH stronger rear end with the modified 8.8. Like someone else mentioned, you can get axles, you can get stronger diffs, but you can't do jack about the ring and pinion, and when you make that the weakest link it's only a matter of time before the teeth get sheered off if you're drag racing. Not only that but i'm pretty sure the housing itself is stronger on the 8.8.