Nakapag-install ako ng VDO diesel tach sa '90 B2200 pick-up about 10 years ago, kasabay ng turbocharger install. I sold the unit some years ago, but remember the installation (cuz it was so damn hard). Click below for a sample of a VDO diesel tach:

http://www.egauges.com/vdo_ind.asp?T...pit&PN=333-952

Meron rin up to 6k RPM, but most diesel engines top out at 4,500 lang yata. Tina-tap yung "W" terminal sa likod ng alternator, kung meron yung alternator mo. Here's VDO installtion guide with alternator tap described on page 2:

http://www.egauges.com/pdf/vdo/0-515-012-037.pdf

Or if you can get an Autometer diesel tach w/ probe sensor, here's the link to installation guide:

http://www.autometer.com/productPDF/608.pdf

And I think the simplest is the ISSPRO diesel tach with pulley-mounted magnets and a sensor on page 16, but the tach is kinda small at only 2 1/16 in. across:

http://www.isspro.com/catalog/ISSPRO...log%202006.pdf

Hope this helps. Cheers