Black wire to battery? Black wire is typically ground, if you wired to negative post on battery that's good. Could also connect to any good ground under the dash. Green to distributor, tach terminal on HEI or negative on coil of points system. Red wire to anything hot when car is in run, their is a IGN connection in fuse block that is a good point.
You didn't mention what type car, year, type of ignition and type of tach so I'm making some assumptions that may not be correct.
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Hank
70 Chevelle SS396(454), M20, 3.73
My Chevelle
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