More wiring: So I bought a power distribution block on Amazon to use as a ground block. When it arrived, I didn't realize it was so big. I should have paid more attention to the size before I made the purchase.
In order to use it I decided to cut it in half. I replaced the top bolt with a stud that I drilled and tapped into a raised section of the firewall, so it's thoroughly grounded. I confirmed the continuity with an ohm meter.
Connected all wire grounds to the bus bar.
Finished product. It worked out pretty well.