Coupe and Sedan headlights aren't interchangeable because the fenders are shaped differently where they join the bumper. You'd have to replace the hood, bumper, grill (with 2010+ coupe parts) and have someone custom make a set of fenders that were built for a coupe at the front and a sedan at the rear. The doors are shaped differently (thats why you couldn't just use coupe fenders too). It would look great if you could do it right, but it just would cost a fortune in custom fabrication to make OEM parts work.
Current: 19" G35 Forged Rays -- Projector Headlights & HIDs -- Factory iPod Connection -- 3.5SE Mirrors -- Eibach Pro Kit -- 30% Tint -- K&N Typhoon -- Mustache Overlays -- LED Tails -- Convenience Audio Controls & Leather Steering Wheel -- Foglights -- Auto-dimming Mirror -- Racingline Strut-Brace -- Ambient Lighting -- Aluminum Kick-plates -- Factory Canadian Spoiler -- SBD Ground Wire Kit -- Trunk Net