Believe me, you'll hear a lot of people tell you 700+rwhp. I've been inside this motors more than most people, and can tell you there are 2 very weak links in these engines.
1. The rod bolts are the weak 8740 bolts and can not withstand the stress of high HP for long.
2. Ford continued to run their super tight piston to wall clearance with these forged pistons, which expand at a greater rate with heat. They did this to eliminate the "piston slap" noise that aftermarket pistons create with looser PTW clearance. They also did it to meet CAFE standards, and make use of the 5W-20 oil. The skirts of the pistons, and the ringlands tend to wear very aggressively in these motors.
With that said, I realistically would not go over 500-550rwhp with the stock shortblock. While there are some out there with more HP, it is a risk that I would not suggest. | 
Stock Engine HP Max 
