Lets not get misinformed here. You would only need a dropping
resistor if you had a 12v system and needed to drop it to 6v.
You Jim, are going in the opposite direction, you need to boost
the 6v up to 12v. Do that with an inverter. Not only will one
of these power your 6v tach but it will power your modern 12v
radio/player or use it to charge up your cell phone etc. Here
is the one I have mounted under my dash in my '50, 3600:
http://www.pbase.com/dennygraham/image/139692811/largeThey're available for about $70. Others rated at higher
output power are available but run over $100:
http://www.ebay.com/itm/like/251192179523?lpid=82Now the tach. The ones made for 6v are quite pricy, like over
$150. With the booster you can use a 12v tach like the small
SunPro 2 5/8" for about $30. I got mine for under the at
Farm & Fleet but here's one at Summit for about the same. It
works just fine with my stock AD truck:
http://www.summitracing.com/parts/sun-cp7906?seid=srese1&gclid=CLLagszB3LoCFQVgMgodsh0AmQInstalled in my '50:
http://www.pbase.com/dennygraham/image/142002156Denny Graham
Sandwich, IL