Look at the wiper control knob on the dash.
The original electrical motor used the same knob and mechanical cable as the vacuum motor.
The kit has a new knob and electrical switch (see picture).
Attachments
54 Elec Wiper 02.jpg (68.46 KB, 105 downloads)

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."