mech diesel tachs

[chevy joe]

i know this is a ford forum but i also own a chevy with the old school 6.2 mechanical diesel. i surfed the isspro site but the descriptions are not very good. im looking for a cost effective tach. could you tell me briefly how the following gauges insall so i can make the best choice for my truck: alternator, programmable, igniton, and mechanical (i assume mechanical runs by cable?) also your suggestions are appreciated