Weakest link are the connecting rods, like the previous gen. Although, the new 5.0 has stronger rods than the 4.6, but not as strong as the gt500.
These hp numbers are RWHP
'11 5.0L Four-VALVE DOHC
Base power on the Mustang's new standard V8 is 412 hp and 390 lb-ft at the flywheel. So far Burcham is making 750 hp at the wheels at 8,000 rpm on a stock motor with no problems. Svinicki says the engines have been very durable so far. Others aren't so fortunate.
Con rods break (600 to 650 hp): Expect the rods to still be a weak link. Overall strength appears to fall somewhere between the three-valve and the Shelby 5.4L four-valves. Although he's not yet broken any rods personally, Burcham has already received reports of some failures.
Piston disintegration (nitrous or high boost): The pistons remain hypereutectic, so don't expect them to last long under high boost or a big nitrous shot. On the other hand, special oil jets enhance pin oiling, making them marginally better than previous three-valve pistons.
Crankshaft: The new 5.0 motors now use forged cranks. No problems so far. Ti-VCT problems (more than 6,500 rpm): At present, Comp is leaning toward a kit to lock out the factory Ti-VCT (Twin-independent Variable Cam Timing) actuation when running serious cams.
Fuel system: On the new 52-psi fuel system, it may be harder to alter system pressure and delivery characteristics than before.
Block: With quality rods and good forged pistons, the Coyote's improved aluminum block can easily support 1,500 hp.
Read more: What Break's in 2005-2011 Ford Mustangs - Hot Rod Magazine