There is a ground wire or braided strap that runs to the firewall usually off an intake bolt or bolted to the back of the head. On my slant six, there is a ground wire from a bellhousing bolt to the firewall. I also added a #4 ground where the battery negative bolts to the block and ran it to an inner fender bolt at the driver's corner of the radiator support just in front of the battery. You need grounds from the engine to the "CAR" like that since the engine is mounted on rubber. I've seen an entire steering column's worth of harness BURNT SLAP UP because the entire electrical system was trying to ground through the column shift linkage. It will ground "WHEREVER" it can so make sure you do it RIGHT or you might regret it.
