I've got the V8 commando emblems on my 65' so can't help you there but like your mockup I believe it sits on the trim ring centerline. You just need the distance back and I'm sure someone will chime in. I dimensioned your pic to make it easier for someone.
Here some measurements for you. My car is in the body shop and was there this morning so I took some pics for you.
My car has the V8 emblem on it, and is a 65 Cuda.