Scourt:
You will note a lot of lookers, but as yet no replies to this topic. This idea has been absolutely beaten to death. No offense, as there are no dumb questions. A bit of searching would kind of let you see what I speak of.
The '06 and '08 are of the same generation, so if the project were mine, and I really wanted to do something with e Gen 1, I would focus on getting the '08 on the road. Anything from the '15 will not work easily with either of the other 2.
I would use what I could from the '06 for the '08, and then sell what is left of that, along with the useable pieces of the '15 to help finance the project.
Know up front though, that you won't make any money, and when you are done, you will still have a 12 year old Charger worth book value if you are lucky.
Another option, would be to find a '14 or '15 Charger 3.6L with a bad trans or engine, and use those pieces from your '15 to bring it back to life. Again, selling the other 2 to help fund that. I prefer the newer body styles, so this option would be my choice if I were in your shoes, and desired a project.
Don
