If your going to keep making your car faster (which we all try to do LOL), you should try to find an 8 3/4 rear end. You could even throw a housing brace and aftermarket axles on it just as some added strength if you have the extra cash.
This may be overkill for now, but eventually you may need it. If your already blowing up that 8 1/4 rear end, then what's going to happen to it, when you get some more HP or hook up better?
Good Luck