Triumph Repair: Spitfire distribtor coversion, thumb nut, ign

Question
I am trying to wire up a Lucas electronic dist to my 1974 Spitfire. I have a late model tach, how do I wire it up to work. My old dist had a cable tach drive for the older style gauge. Thanks

Answer
Hi Charles,
Look on the back of the tach. You should see one flat spade connector plus, either two pigtail wires (white & white with a black tracer) or a small white plastic block held in place with a square "U" shaped metal strap with a small threaded post sticking out with a brass thumb nut holding it on. If you have the tach with the two white wires, they are the power "in" and "out" to the coil. If you have the type with the "U" shaped metal plate, the coil supply must make a loop around the plastic and "U" plate before going to the coil. I know without a sketch this may be confusing so let me know which kind of tach you have. The one flat spade connector on either is a "Ign On" power supply and be sure to ground the tach case if you harness does not have a ground to it.
You can contact me at fitzcharlesh@bellsouth.net if you need me to e-mail a sketch.
Howard