I truly do not know if it works or not how can you test a tach
Good explanation that I have stored in the clouds...
Tachometer Testing
Look closely at the back of the tachometer, you can see the markings as to where each lead needs to go (COIL, GND, 12V). Tachometers are very easy to hook up and test on an V-8 engine, especially if you have one around with an HEI distributor (HEI's have a 'TACH' terminal right on the distributor cap). If you have anything around with the old points distributor, then the terminal marked COIL on the tachometer goes to the (-) side of the coil. The 12V terminal of the tachometer and GND terminal are self explanatory, you need any 12V power source and a ground. If you do not have original wiring pigtail then a .250 female spade crimp-on connector on the end of a wire works fine. When tachometers start to go bad they read high, like 1200 RPM at idle, and get worse as the RPM’s increase. Having a known good tach in the vehicle to compare it with is a real plus. At idle you should see 500-800 RPM and a quick tap of the throttle should see 2500 RPM or so. As some go bad the needle responds very slow to RPM increases or it will “stick” as it moves forward. When they really get bad they will bury immediately or not register at all.
edit: link...
http://www.73-87.com/7387garage/interior/factory tachometers.htm
