I have a tach that I can't get to work with my MSD 6AL. I've tried straight up, no-go. So I put in the MSD adapter and still nothing. Since my 68 GTX was assembled Frankenstein-like, I'm not even sure if this is the right tach. There are three wires attached to the back (excluding the lamp) I believe they are ground, 12V, and then line-in for want of a better term. The wiring diagram for 68 only shows two wires. It worked before the MSD swap. There is a repair kit someone sells on e-bay that swaps your tach internals. Does this work? A new tack is just shy of 200 bucks. And the kit is $75. Thanks

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