To get accurate measurements, use the 10" dimension to scale.

Note that the front water pump pulley extends past the line of the bulkhead behind the driver.  There's a small fiberglass "bubble" between the seats that covers it.  The horizontal teal line through the top of the engine is an inner panel with a large hole to let the carbs breath the air that is ducted into the volume below the rear window.

The shallow box on the bottom surface of the body above the transaxle are reinforcing lips surrounding the air vent.