I did this on an old build "New year, new body". Tried to copy the link below, not sure if it worked? American Powertrain makes a kit (American Powertrain Hydramax Hydraulic Clutch Release Systems HMGM-01101G). Comes with everything you need. Bolts right up to existing pedal.
http://67-72chevytrucks.com/vboard/s...d.php?t=753110