The Ballast Resistor was used ONLY to reduce the voltage to the points inside the distributor while the car was running. When the car was being started the resistor was bypassed completely, and 12v was fed directly to the tach and then the coil.

In the schematic you posted, simply connect the Green/White wire to the Black/White wire on each side of the Ballast Resistor to each other. Tape it off and you're done.

E

I have an original 1972 240Z that has done the same thing since I purchased it in 1980. Mine seems to be related to the temperature of the top of the dash. When the dash is hot to the touch, the tach reads so high that it's a wonder it did not break. Over the years I learned that if I was going to be parked in the sun I put a towel over the dash. I know this is a pain but the tach still works today and the other benefit is that my dash is not cracked.