SVT has more than just engine/body kit.
SVT Duratec has 30 more HP, some of which you can gain easily - SVT intake manifolds & throttle body along with an upgraded catback and intake but some of which is harder to duplicate - hotter cams, ported/polished heads, ECU upgraded (to bigger injectors, more spark advance, no speed limiter), minor improvements in compression.
SVT has beefier clutch and lighter (only 2#) flywheel
SVT has thicker radiator core and adds oil cooler
SVT has bigger front brakes and an upgraded ABS system
SVT has custom tuned suspension (not stiffer than SE but understeer reduced & well balanced), 16" wheels and much better rubber
SVT interior, perforated leather seats with extra side bolsters, white face gauges, special floor mats, sunroof on most
SVT airdam with increased air to radiator, side skirts, rear facia
And, its one of the least expensive truly limited production cars you will find.