Glad I still have an outdoor day job and get computer use at night.
I think I am going with a Tiny Tach for the diesel on mine. Just easy to do as I don't have that W output either. I don't have any problems with the current alternator so am not thinking replace that with one that has the W then find a tach. Tinys are about 100 bucks though. About as much and changing the other components out to get the same information.
Looking at the clamp on model. It comes in both the 6 and 7 mm clamp types. I think we go with the 6 but I haven't actually measured it yet. Anyone know off hand?