"The research I have looked at seems to say it was optional."
Where did you hear/read that?
Do you see the attachment holes for the switch?
Are there any loose wires nearby? If not, someone will tell you where they run. See if you have loose wire that run from the tail/brake lamp towards the front of the truck. Trace that/those wires to their forward ends.
Before you drove the truck, was it inspected?
Do you have turn signals?
Is your truck 6v or 12v?
