Stainless Steel Brakes (http://www.ssbrakes.com/) makes a front disc brake conversion kit that uses your original spindles. I am installing one in my father's 66 Mustang (I know, but they didn't make Cougars in 66 : ) that is some sweet so far.
The kit includes the PB booster, dual master cylinder, lines - everything you need. I would look at them for the rear conversion as well.
I put the Baer brake kit on the front and I know they make one for the rear. They can set you up with a great kit and some technical support. It was easy to do as well. Plus you can getthe big 13 inch cross drill and slot. The price for mine was $995 including the proportioning valve, which is comparable to the SSBC kits. The only catch is you have to have some big rims to getthem to fit.