Try Google,typing in "signal stat wiring" there's some diagrams there that tell how the add on kits hook up.
speed
PS-it's fairly common for the old stop light switch to be disconnected,due to the tendency,once worn over years'time,for the stoplights to stay on and run the battery down. That was the case on my '57 GMc;I hooked it up and it worked great until the next heavy rain,then the battery went dead. finally tracked it down to the stoplight switch getting wet and the contacts inside bridged during the night,running the battery down. I recently changed it over to a micro-switch;it's weather-proof.
Speed
