The 7 ¼ simply not hold up to any load you put on it with your engine.. It may hold up for a bit if you are VERY easy on how you drive and never get on it.
In short…. A 415hp/440 backed by a 7 ¼ is pointless…… In a drag race against someone walking the person walking would win….. Because your car won’t move with an exploded rear end.