Dan, Yes the direction of the loop does matter. And it requires a different direction depending on the polarity of the car. I had not understood that at least one of your tachs was from an SIV. But shoulda tried reversing the loop! Nice work Sunnby and Dan. I did not follow 100% what you described in the wiring, but it's clear that you ended up with one current path from Ign switch to the coil and that path loops in the right direction thru the pick up on the rear.
Based on previous experience I would guess that your tach will read about 50% high. A few of 45 year old parts are critical to teh accuracy and almost surely have drifted pretty far from original value, especially the timing capacitor and thermistor. But at least you have it wired correctly now.
Scott , yes it is possible. Just use a 12 V power supply and an accurate signal generator,with a 50 ohm output impedance, that can put out a 30 Hz to 200 Hz square wave with about a 30% ( or lower) duty cycle. Wind about 30 turns of small wire around the Steel U-clip, and connect the ends of that 30 turn loop to the generator ouput. Set the generator to the desired frequency (RPM/30= Gen Freq)
900 RPM = 30 Hz, 1500 RPM = 50Hz, 2400 RPM = 80 Hz, etc.
If you just want to "test" it . Use your car. Connect some test leads from +12 somewhere on the car to the power spade lug and a second lead to connect ground to the case. Disconnect the white lead from the + terminal of the coil and route it thru the U clip on the rear of the tach and reconnect it to the Coil +. ( leave the plastic piece on the wire, right where it is inside the car. It's not needed for a test. Start the car and see if it works.
Tom