Ok I will jump in here since I think I can offer you some ideas (or maybe some inspiration).
I built my clone back in 1992 from a base model 70 Road Runner 383 4 speed coupe or "post" car - not the correct hardtop model.It took me about 5 years to collect the correct wing, steel nose and such to put the car together. Now you can get the stinger kit or other parts to use fiberglass or really save up and locate a repro steel nose.
I would suggest a road runner if possible. It would have the rallye dash 8 3/4 rear correct "trim level" a big block. Plus IF you abandon the project or even possible sell the car, it could be converted back to a Road Runner - with 4 holes in the tops of each quarter panel where the wing bolts went in. Still, it is a Road Runner and worth more in the end than a satellite or Belvedere.
You will have a better time finding a Satellite though and buy in cost will be a lot cheaper. You would not have modified a "real" Road Runner and will keep the purists happy. Some did have at least an 8 3/4 rear axle and up to a 383 HP motor so that is a bonus.
You will be selling the front clip off anyway so don't worry on the front half of the car. If you are buying a car, I would recommend buying a running driving car if it is important to drive it while you continue to collect parts. You will be meeting other guys in their rides and just get to enjoy it as a base car before the conversion - doing stuff like brake rebuild, suspension, electrical and so on.
I did not do the rear window conversion on my car. And, being a post car hurt the value even more as far as a correct conversion. But I drive it weekly - sometimes every few days. And I got Richard Petty and his cousin Dale Inman to sign it last year. And I bet 90 % of the people dont even care if it is real or not - it is on the road where it belongs.
My point is, you can get a driver to enjoy while you are getting up the special parts. Enjoy whatever you build it is your car. Don't listen to the negative people. You can do it - just think a few steps ahead - make a good plan and don't lose interest.
http://i960.photobucket.com/albums/ae81/myaerocars/PettyVisit2005_zps7ee02576.png
http://i960.photobucket.com/albums/ae81/myaerocars/Chargerpics005.jpg
http://i960.photobucket.com/albums/ae81/myaerocars/Chargerpics007-1_zps41b3613d.jpg
Good luck and stay focused and upbeat. You can do it.
Godspeed,
JON