Read the earlier thread today concerning "dealer installed" hood tachs.
Having owned several factory equipped hood tach '69-71 A-bodys, thought I'd link some pics & comments*concerning Factory hood tach installs. This is for those that own a factory hood tach '69 or '70 GTO or Tempest or LeMans and the factory hood no longer exists. Many of us that have been in the hobby a long time have all pitched a rusty kinked GTO. For 1971 GTO & LeMans factory hood tach installs, all the factory dimensions are in the 1971 Assembly Manual. Am working on creating my own '71 installation artwork, as the factory artwork is barely legible in certain areas.
The first thing to note is the '69-70 hood tach hole when added at Fisher Body
Note the hole is very clean as a hydraulic type punch made the hole. A hydraulic sheer also took a bite out of the brace directly behind the hole.
The above was on an original '70 hood tach hood. Having owned several '69 GTO's with factory hood tach holes the trimmed area in the brace is the same. I cannot personally vouch for the trimming of original '68 GTO hood tach hoods as there are several underwood bracing versions of the '68 hood.
...Another factory hood tach hole
Next, Inline Tube's YouTube video:
The hole saw method works very well if one is very careful. Hole saws are also much cheaper than a Greenlee 3 3/4" punch out tool.
NOTE @ the 1:00 minute mark of the video, the completed '69*hood tach install looks very nice, but there is no factory relief on the hood brace. Sure makes one wonder if the hood tach is positioned slightly forward than a factory install. If nothing else, the lack of a relief in the brace will draw the eyes of very experienced Concours Judges.
For those needing repairs of their original GM hood tachs, Randy Watson is the best. Have used Randy's services in the past & about to send him another hood tach to go through.
Hood Tach Article - RC Tach Shop
Having gone through the recreate the factory hood tach hole process several times, am just glad to be able to pkg all the above info here in one post.