The back side of the bottom emblem has a rubbish backing. The others nothing. What is correct, before mounting these?

 

If you're putting these on a C2, the Stingray emblem is wrong. For a C2 it is "Sting Ray", two words

I feel the issue here is that the Stingray emblem is for a later Corvette and so uses a different mounting method.

 

The Shark emblem used two sided tape.

 

Here is the trick to put them on without the nuts on the back. Why you ask, because the nuts are very difficult to put on due to access. Take a small piece of painters tape and put it on each post. Test fit for snugness so there is resistance. Second reason, you can remove the emblems to wax tour car. Dennis

 

If you use the pins, always preinstall the self-threading nuts and then remove and reinstall several times. This cuts the threads while you have good control making it much easier to install the nuts when the emblems are in place and you have little control! Also, get the correct emblems for your year C2.

 

you could also use barrel nuts. they push in the hole from the outside, then you push the emblem into the hole. you can remove the emblem after but it's tricky. you have to be careful not to scratch the paint.