I have a 2004 Sebring convertible and a 2006 Sebring convertible.How closely will parts interchange from the electrical systems , heating and AC,body, drive train,etc.?...You get the idea...

 

Pretty much everything should be interchangeable, as far as ordinary stuff goes. However, look at the engine computers. There was a change to the engine control system during the '04 model year, and the plugs on the new computer are different. If both your vehicles have the same plugs on the computer, then your '04 should be the same as your '06. That's not to say you can swap out the computers from car to car and expect them to work. To move a computer to a different car, it would have to be re-programmed with the correct VIN and mileage.