Hi Scott,
I can't get a front pic that really shows anything.
The tach cable exits the rear of the tach drive, low on the LH side of the engine, goes straight back toward the extension panel, sweeps up through the panel flange slot, & curves over to the tach. It is about 33" long.
The speedo cable exits the drive on the RH side of the transmission heading forward, makes a gentle curve across the top of the transmission, curves upward through the same slot as the tach cable, & curves over to the speedo. It is about 63" long.
The top of the extension panel flange, shown in the pic, is indented enough to allow the two cables to pass through side by side. A small bit of sealer around the cables will provide an air tight seal. The extension panel is the piece that fits between the the inner edges of the footwells & over the transmission hump.
D
The big access hole in the firewall leads to an inner flange & nut which is used to secure the bottom heater mounting stud. See if the attached sketch helps.