I must be getting old. Nearing the end of a resto of a '68 cuda and am fishing things through the firewall. I seem to have an extra 1" hole above the voltage regulator and behind the wire loom (see in photo). I have already run the e-brake cable, the speedo cable, clutch rod and the M/cyl. I am dumb, I can't remember what goes through this hole. Help! Thanks.