got wrong flex fan on ebay..DAMN!!!!!

Is it blowing air out of the engine compartment across the radiator and out the front of the car?

If so, you have the potential to overheat the car. At some speed, the air entering the radiator and air the fan is trying to blow out are gonna sort of cancel each other out - leaving very little air actually flowing across the radiator.

I'd get the right fan on there.

It's easy to be confused. The stock Mustang water pump is considered 'reverse rotation' because it turns the opposite way of the crankshaft. So, do you have a standard rotation pump, and you ended up with a normal 'reverse' rotation fan for a 5.0? Or do you have a normal reverse rotation pump, and you ended up with a standard rotation fan?