If you're talking about just up through GT models, the new 2011 5.0L V8 is the biggest. It produces 411 horsepower, the most powerful GT Mustang ever built. If you're talking about ALL Mustangs, the most powerful and big would be the 5.4L Supercharged V8 available in the Shelby GT500. It produces 445 horsepower. And it is SUPER FAST!!!!!!!
The biggest engine in size was the 1969-70 Boss 429 Semi-Hemi
The Ford Mustang GT has a V8 engine, while the Ford Mustang has a V6 engine.
The 2006 Ford Mustang has a V6 engine.
The 2014 Ford Mustang has a V6 engine.
The 2011 Ford Mustang has a V6 engine.
The 2003 Ford Mustang has a V6 engine.
The 2005 Ford Mustang has a V6 engine.
The 2009 Ford Mustang has a V6 engine.
The 2004 Ford Mustang has a V6 engine.
The 2010 Ford Mustang has a V6 engine.
The 2008 Ford Mustang has a V6 engine.
The 2002 Ford Mustang has a V6 engine.
The 2001 Ford Mustang has a V6 engine.