Disk brake cost?Junk yard?

How much do u guys think a disk brake set up would cost me from the yard?My dads budy said he just pulled stuff off a 73 dart with disks on her,hes goin back later to look at whet the shape is like on them,whats a good price for them if iwas gonna get them,more less just the spindles cuz there hard to get sometimes
MIKE