If you want to know the specifics there's an article at
www.bigblockdart.com that gives pretty good detail, and there's another but I can't remember the URL. There are a ton of posts about this swap as well. Basically you will have to have(depending on year) upper control arms, larger lower ball joints, disc brake brake hoses, disc brake spindles(don't have to be A body in my opinion, others disagree),calipers, and a disc brake master cylinder(as I said, this is compressed, there are quite a few other pieces and this swap can range from $0-$600, $600+ being where you have mostly new parts and start upgrades/rebuild front suspension). I think my swap ran around $800 but that was almost everything new with upgraded torsion bars and including wheel alignent and playing around with tires. I had to play with tires because I originally had a 4 inch bolt circle, all newer model disc brake systems will be a 4.5 bolt cirlce.
If you decide to do rear discs they have pressure regulators and MCs specifically designed for 4 wheel disc brakes, if you go with the 10 inch rear drum brakes you can keep your MC. To get 10 inch drums it'll be cheapest to find an axle with 10 inch rear drums, preferably find an 8 1/4 axle. They will have 7 1/4 10 inch rear drum axles but if you're changing axle you might as well upgrade.
The biggest thing to remember in doing this is that you do it slow and methodical, the suspension is easy to work on but if you do it wrong the consequences are more than a blown engine. Torque everything down to spec, and if it's hard to get at with a torque wrench keep trying till you get it. Also, when rebuilding a suspension save yourself a ton of time and rent a suspension kit rather than using a pickle fork.
-Shivadart