I have a '96 F150 XL & am installing fog lights.
Switch installed, relay installed, battery connections installed.
My question is, where is a good place, (preferably passenger side), to go through the firewall?
I have a three pin connector, so the hole has to be about thumb size. . . .

 

Add it to the blower fan harness passing through the blower case. De pin the connector so it is easier to pass through.

 

Not on passenger side, but the clutch block off plate on auto trucks is a great pass through.

 

I went through drivers side:
dash switch
-->firewall
-->relay
-->-->fog ligths
-->-->batatery