Years ago I put a cheap JCWhitney 2-1/6" tach in the dash of my '66 Toronado, in place of the factory clock. (More than a decade later, Jay Leno did the same thing with a boost gauge. ) The tach has long since died, and I'd like to replace it with a slightly larger 2-5/8" unit. I'll have to mill out the potmetal dash pod for it, but that's part of the plan. Problem is, the car's a daily driver with a very mild engine build and tall gears- 60MPH is only about 1800 RPM. I'd like to use a 0-5000 tach, rather than a 0-8000, but the 5K ones only come in "diesel only". They apparently have a sensor or pickup that attaches to the alternator somehow, to feed the signal to the tach. Is there a way I can use this (or one like it) with a spark ignition? (HEI, in this case.) I don't know what the sensor/pickup is or does, or what kind of signal the tach needs to properly read. Over a hundred bucks is a bit much to just buy one and try it out, so I'm hoping someone here can help me out. Doc.