The dimensions in the A.I.M. are quite accurate, but are only useful if you have a body shell or panels set up on a surface plate to datums defined by the GM Body Grid Measurement System, specifically for body measurements. Those dimensions are based on a point on the firewall being "0" fore-aft in the side view and a point below the rocker being "0" vertically, with all points rearward being positive and points forward being negative, in five-inch grid increments. SV = side view, FV = front view, RV = rear view, PV = plan view.
They worked fine in assembly plants to build drill fixtures once a body set up on a surface plate was marked-up based on the grid coordinates, but are of little use otherwise; that's why the best way to locate emblems is as Jerry mentioned, by making tracings or templates from a finished car with correctly-installed emblems.