Barrel Clips for Fender Emblems

OK, makes sense. My car didn't have these, so no holes yet. These are OEM 360 Four Barrel hood emblems for '72-74 Challenger. I was considering putting them on my '67 Dart front fenders when I do the 360 Magnum install. They still have the plastic barrel nuts on them. Anyone know the I.D. of those holes on the Challenger hood? The O.D. of the plastic bit is 3/16", but I see your point, it has a slight indent closer to the back of the emblem, the sheet metal must seat in there to hold it tight against the surface.

So, not sure I can get to the back of the fender for both posts to use standard nuts that cut into the posts.