Hi - I've got a '67 Johnson 60 hp (model VXL-13A) with the alternator under the flywheel. I'm looking for a tach but not sure which would work. Some have a selector on back to choose a 2, 4, 6 or 8 cylinder motor, and some have selectors for the number of pulses, like 1, 2, 3, 4, 5, 6, etc...