Did some measuring today for the 340 4 barrel emblems.
Measurements were all taken using a cloth tape measure that was pressed to follow the shape of the hood.
First measurement is from clipping the end of the tape to the rear (windshield side) of the front hood and stretching to the hole that is closest to the windshield. That measurement is 19 ¾ inches.
Second measurement is from the driver’s side edge of the hood to the front pin hole (on the front grill side of the hood) This was 5 7/16 inches.
Third measurement is from the driver’s side edge of the hood to the back pin hole (on the windshield side of the hood). This was 5 3/8 inches.
Take a look at the images below and this will make more sense.
The emblems I have the pins are 4 ¾ inches apart.
Hope this helps.