I bought the same kit from Manes Truck parts. Everything was fairly well made and it went together pretty easily. The printed circuit from my kit fried the first time I powered it up (it had a manufacturing flaw) but it was replaced at no cost. I'm not sure about their comment on it NOT working with HEI. I have HEI and the tach works just fine. Maybe there are different versions out there? I wouldn't hesitate to recommend the kit from Manes nor would I hesitate to recommend Manes as a source for parts. Manes also sells used parts which is great since some items are just not available new. They offer responsive and helpful service and reasonable prices vs. other sources.
Another thing to mention is that the tach conversion kit kind of assumes you already have a cluster with gauges (oil pressure, temp, amps) because it provides holes for them in the housing and the bezel. If you have the basic cluster (speedo and fuel only) you will be left with empty holes in the cluster unless you also buy gauges. The new printed circuit also assumes gauges so would not be compatible with the more basic cluster.
The Manes version:
http://www.manestruckparts.com/store...Category_ID=20