A-body Disc brakes
I will add a small piece of info here that may be of interest. If you seek out a 77-79 B body or a 79-81 R body and get the cliper adapters from one of these with 11 3/4" discs ( I got mine froma 78 Magnum if I recall correctly) the adapters will allow you to use an 11 3/4 inch rotor with the exact same calipers and pads that you would use for the smaller 10 1/2" rotors, and gives you huge bullet proof fron brakes. It is what I currently run on the front of my 73 you see pictured here. Rotors are also still available brand new also, as they are the heavy duty parts that all the taxi's, cop cars, etc. came with. I will try to dig up my reciepts for my rotors to give you a source but I am pretty sure I bought them at Pioneer Rim and Wheel here in town. Like I said, you can still use the same calipers and pads so no searching for that stuff.
There is a little info on this on the BB Dart web site, but I rarely suggest that site to people as I feel the majority of those guys have serious attitude problems, something to do with the belief that because they have a BB in their Dart they are the only ones who know anything about these cars and they generally behave like children in my expierences with them, BUT their is some good tech their. Here is a link to the specif page I am refering too, ---->
BB DART brake tech page
I know there are other sites that cover this info but if anyone wants more info about it or needs a picture that shows the difference between the caliper adapters to make it easier to identify them when searching for them, just let me know and I will be glad to send you what I have on the subject.