And if it doesn't have them I would definitely recommend putting them on because of the amount of traffic and every other car having them and having to make a panic stop you'll definitely appreciate having Discs. Here in NY a slight hill on a parkway and everybody is stopped on the other side that you didn't see till too late.
70 and 71 will fit for sure. 72 is a transition year if my memory still is accurate. Rock auto has parts and some are actually rebuilt with factory numbers, but most are Chinese knock offs.
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If you don't care about factory original, there are numerous after market kits that will bolt onto your spindles. Disc brakes are definitely better on the front in my opinion as they force the tire and wheel into the pavement and have much less fade resistance, especially when warm.
The Californian Highway Patrol started experimenting with disc brakes in 1964 and bought 500 cars with disc brakes in 1965. So I figure there's a good reason for disc brakes if the CHP spent time and money on them.
My 70 Challenger had drum brakes which I converted to 73 disc brakes because I had the parts. My 71 Barracuda has factory 71 disc brakes. If I had the options available now, I'd go with any 11" to 12" disc brakes. I have a kit to mount disc brakes on the back of my 71 Barracuda, but I can tell you from owning a 98 Dakota with rear drums, the rear brakes don't do a lot for braking as I only replaced the shoes two years ago!