The "Camaro" script and the "By Chevrolet" block lettering was different though they look very very similar unless put side by side.
There was a difference in the positioning of the location pins as well. I'll dig mine out and post pics.
With today's reproduction, I strongly doubt that each one of these emblems are being reproduced as two separate emblems. Since they look similar (to most) it's just cost effective to produce one design to use in both places, the header and deck lid.
Another reason to "measure twice" and cut once. If your using the reproduction emblem of p/n 3916654 and your not shooting for factory correct then use. But I'd suggest to pick one point on deck lid, then caliper the pins of the new emblem at center-to-center or as stated earlier, use a lipstick of sort and plot on paper. Use as a template.
Or you can find the factory 'Fisher Body" emblems on ebay. I see them all the time from $15 to $25.
Pick your poison...lol