We've discontinued the tone wheel kit in favor of using the waveform (W) terminal on the Delco 28SI alternator in combination with the Dakota Digital Diesel Tach Interface (https://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=1192/mode=prod/prd1192.htm). This solution has proven to be a great alternative given the added benefit of that alternator's internal regulator, high amperage rating, strength and low cost.