I am just finishing up installing 4w disks on my 67 k20
And am using a master cylinder from a 80 vette with a pv4 valve
Just make sure your using a booster with a short push rod (almost flush with booster face)
Not sure what a 71 came with
Here is link I found helpful
Fyi 14 bolt disk parts bolt up to an Eaton also
Good wrenching
http://www.fourwheeler.com/how-to/su...o-disc-brakes/
Apologies for the pic rotation