Four doors are definately cool. The only problem is the resale value. I have so many cars I'd love to build if I had the time and money and for my four door I envision a Volare' or Aspen. Find one thats as stark and basic as possible and build it to look like domething the FBI might have used back in the 70s. Go with a basic color like gold, green, or light blue, just stay away from anything that's too bright or attention grabbing. Has to have V-8. big or small block but no visible speed equipment so that means no big headers or oil pans hanging down. Needs a vinyl interior with a color match to the exterior, stock radio, column shift, only factory gauges. Use 15' steel wheels with dog dish caps and black wall tires, same size front and back and the finishing touch= a police two way radio and one of those very long whip antennas with the spring at the bottom mounted to the rear bumper and pulled in an arch over the car and the tip tied to the front bumper. Has to have enough power to incinerate the tires easily. Yeah that'd be my four door.