If you follow the wiring harnesses to the firewall on both sides of the engine there are large rubber grommets that go through the firewall. Both of them have a small hole above the harness that you can add a wire through.:tu:
I went through the grommet just about a foot under the glove box on pass side, behind the carpet. I installed an air pump with a wireless controller. Needed the controller to be in the cab, for protection from the elements. You are going to need to literally crawl onto, and into, the hood cavity. Have an LED headlamp and a good pocket knife and you will be fine. I needed to shave a bit of the rubber off, but it is back to being totally sealed. depending on what you are working on, I could send you pics of my mod.