There is already a way through the firewall.
The original windshield washer pump has three rubber tubes passing through a grommet. Most people have (or will) replace their washer pump with something more modern under the hood. That leaves that same grommet as a gateway through the firewall.
This is the route I'm going to use to mount my forward cam, fog lights, and laser pointer.
Why a laser pointer? To aim my truck's forward cannon and machine guns, what else?
*The plan is to use a laser pointer to help align the truck to go through my ultra slim garage door.