well...my trip to the shed wasn't entirely successful. The measurements are shown below but it seems that, on this car at least (which I had thought was largely original), the emblem is mounted too low. On my ute (which isn't here right now for me to look at) the emblem is definitely higher, more like the 26mm Alex referred to.
So, it might be best to check another car or three first but then, maybe just add the appropriate amount (16mm?) to the vertical measurements below. This diagram should at least give you the relative positions of the holes. Note the 2 central ones seem to go through the bonnet and the bracing below so it might be 'interesting' to get that lined up nicely.
Jonno