Seems simple enough. I stopped in at advanced today to pick up a pressure sensor and they had two. One was for cars with a tach and one for cars without. They looked about the same, but the electrical termination was slightly different. One had a clip-looking thing and one had a standard thread with a nut. Any idea which one to use? My car had a tach but it never worked, so I can't remember if it was connected. Also, I changed to an HEI and never used the "Tach" terminal, so how would that effect this sensor? I'm a little lost. I assume with the wrong sensor the gauge won't be accurate, if it works at all.