It's magic man!!!!! Geeze see how defensive they get when they mount a big ass tach on the dash, Those holes for the screws increase the resale value at least 20%.
I mounted mine where the radio was located. I had a monster tach with shift light, one oil pressure light and one temp light. I made a bracket out of 1/2 mild steel tubbing and ran it back under the dash to the fire wall and bolted it with to 5/16 bolts. I made a plate out of 18 gauge sheet metal that was about the same witdh as the radio hole and used some windlace and glued it around the cut out so it looked nice. I bought to 3/8 chorme plated allen head screws and bolts then boled the cut out over the old radio hole. The 1/2 pipe ran through the cut out through a hole in the center and then i made a bracker for the tach and lights to mount. If i could figure out how to send a picture, i would send you a picture of it. Ive been three days trying to sent 6stang7 a diagrahm of a cluth set up. If you want a pic let me know and ill try to figure out who to resize it for you