On my LHD '34, the T-Bolts are exactly 11 inches apart center to center. They are exactly 2 inches (center of bolt) from the top vertical of the firewall. As seen in the attached picture, the T-Bolt on the right is 1-5/8 inches (center of bolt) from the right edge of the firewall. The hole for the speedo cable looks to be 3/4 inch in diameter and is located right above the lower lip of the firewall and 1-1/2 inches (center of hole) from the right edge of the firewall. I'm not sure but the hole for the speedo cable on my car may have been enlarged, or maybe not....
BTW - My car did have the dimples on the firewall for the correct bolt locations....
