Before Shelby GT500 Job One even starts down the assembly line, Ford Racing Performance Parts is hard at work building speed parts for it, based on the company’s Performance Packs for the three-valve Mustang GT. There are three different versions for the GT: the Power Pack (PN M-2005-FR1/FR1A, $899) consists of mufflers, a new mass air, and performance calibration; the Drag Pack (PN M-2005-FR2/FR2A, $1,399) has gears, shorty headers, a 90mm mass air, and performance calibration; and the Handling Pack (PN M-2005-FR3, $1,149) has springs, shocks, antisway bars, and a strut tower brace. (The above part numbers are for ’05 Mustang GTs—substitute 2006 in place of 2005 in the part number for ’06 models). There is also a supercharger available for the GT (PN M-6066-463V, $4,995 in black, PN M-6066-463P,…