Does a 2005 Shelby Gt 500 complete engine fit into a 2003 Mustang?
fit? yes. run? =red tape Best thing to do would be remove the computer from the shelby and swap it out to. Superchip tweeker system may help you adjust the old mustang computer in a fashion that would operate the new engine, but i doubt it. The tweeker systems offer you a laptop view of fuel and air systems, and allow you the ability to shut off or turn on sensors that may affect the runability of a newer engine, on an older computer system. Good luck, I know it has to be killin ya ready to get that thing in there........lol........I know it would be me.