what calipers do I need????

I recently found a set of spindles with upper control arms to put disc brakes on my 70 duster BUT they didn't come with the hubs, rotors, or calipers. Seemed like a good deal at the time of purchase but now I don't know what calipers or size of rotors I need. Also, will I need to find different hubs or can I use my old ones (small B/P)? Thanks in advance