I got the same measurements on my 67. As Rowdy said, the firewall on the passenger side "curves" toward the rear. If you were to follow the vertical plane of the firewall down on the pass side, then the measurement to the point of that intersection is 14 3/8:.
I have a small block, but assuming the bell housing falls in the same place, I measured to the firewall from the bell housing parting seem. There is a lot of curvature on the firewall behind the engine. To give a consistent reference I measured from the top driver side trans bolt location to the firewall at the top of the throttle linkage bracket, the part the bolts fixed to the firewall. That distance is 2 1/2 inches.
I have a small block, but assuming the bell housing falls in the same place, I measured to the firewall from the bell housing parting seem. There is a lot of curvature on the firewall behind the engine. To give a consistent reference I measured from the top driver side trans bolt location to the firewall at the top of the throttle linkage bracket, the part the bolts fixed to the firewall. That distance is 2 1/2 inches.
