Yes the rods should fit the crank. As long as the bearing size is the same. However your problem will be that the pistons will never reach the top of the cyls. The B16 uses a shorter deck height than the B18. You would have to use custom pistons that make up the diff in deck height to reach the top of the cyls and compress the gasses. That will make a heavier rotating mass and negate the benifits of the shorter stroke.