I actually got those same directions and id the conversion several years ago and they work awesome. Just not enough consistent vacuum in a Z/28 motor to make these work. I had a RZ Z/28 by the way.
CAN ANY ONE TELL ME WHERE TO FIND A VACUUM LINE DIA. FOR THE 68 RS
1969 Z/28 Daytona Yellow/Yellow Houndstooth, Tilt, Fold Down Seat, - POP
1969 Pace Car Original & Highly Optioned - Chassis Broadcast Sheet