Rear end advice for racing with a 4 speed

You can buy parts to make a 9 inch WAY stronger than a Dana. Fact.
And the cost would be similar if talking S60 and such a 9 inch.
Well, I ran high 9's with a 60 and the only things done to it were aftermarket axles and a rear cover that had bearing cap supports. Before that, a car that ran high 10's with a 4 speed that was launched at 6k using stock axles and no support cover. So why spend the extra bucks to beef up a dang 9??