You can use the standard tranny tunnel with a CA18DET conversion, all i did when i had my coupe is cut about a 25-30cm square of the top of the tunnel, from the shifter towards the fire wall, the shifter is about 50-60mm back from the standard position. As mentioned before it is a tight squeeze, its hard to put oil in the gearbox unfortunatly, drop the gearbox is the only way, Automatic tunnel is bigger than the manual tunnel.