Well Crap it needs it all!

BillGrissom said
Your 9" drum parts are very cheap and available. 10" rear drums are the hard part to find, but you don't have. 9" drums work fine for normal driving (drove 69 Dart with them for 3 decades). If you desire front disks, the Scarebird kit is affordable and easy to get parts later. Rear disks are just for show, rear drums work just as well. Any mechanic can work on drum brakes. They are the standard Bendix design used in a gazillion cars. But so could you. .

I agree. No need to go crazy here. You don't need to change the rear end and suspension parts, and think you absolutely have to have 4 wheel disc brakes. The pulling you are experiencing can happen with drum brakes, sometimes they can be a little "grabby". Disc brakes are much more forgiving. There are factory service manuals available on this site for reference.

My first instinct was to go to Rockauto. Drums, shoes, hardware kits, etc. You may not need everything but if you have leakage from the wheel cylinders or rear axle seal, you'll have to fix that. Brake pads + oil = wheel lockup. If you want to upgrade, read here first.
http://www.moparaction.com/Tech/archive/disc-main.html
If this is not your everyday driver you can start accumulating parts to do one of these upgrades. No need for monstrously heavy 11" rear drums on an a-body. They'll decrease your gas mileage and actually slow you down when you are accelerating especially with a slanty.

I see you are in Ohio. Ha! rust city, I deal with it all the time. If you start replacing wheel cylinders don't be surprised to find that the brake lines will want to twist off with the fittings. Usually it turns into a domino effect.