Tim, you been waiting 2 weeks on a reply. In 1967 H-D figured the way they had wired the starting circuit had too much voltage loss to properly energize the solenoid. They went to Delco-Remy and picked a part from stock
and incorporated it into the system, they offered a retrofit kit with the wires needed.
Today you can buy a replica of this relay fairly priced, or hang tough & find one with a Delco-Remy cover for about $100.
Go to E-bay and search 71455-67 in Antique & Vintage parts/Harley-Davidson
Tonight they start @ $23.00 plus freight to a real Delco for $99.00
You can attach the relay directly to the bottom of the battery box, or use a piece of 3/4x3/4 (thin) angle about 2" long. (hobby shop, I used Stainless angle) Run a Ground wire to one of your mounting screws, the battery box is fairly insulated.
Beware, they will 'ding' you in AMCA judging.
Perry Ruiter has (or did have) the Shop-Dope where to mount it on his site. It's a fine line, too far in will hit the starter studs, too far out hits the kicker lever.
You will add 2 wires to your bike, one hot to the relay, one from the relay to the solenoid post, then hook the grey wire (faded black) from the button to the last terminal.
old harley parts are MY 401K!