1971 with drum brakes in front, I didn't know there was such a thing.
I have a 1969 C10, I put on it 1971 donor front disc brakes and spindles with new 1971-72 ball joints and steel brake tubing, and 1971 donor rear drum brakes and new 5-lug conversion rear axle shafts. I did manual brakes. The master cylinder bolts directly to the firewall.
http://www.67-72chevytrucks.com/vboard//showthread.php?p=9167631#post9167631