I can't find the part number in my parts book - I have the Oct 1970 version of the 58-70 book - part number is 3399962- note one emblem is missing one post - pm if interested

Anyway I believe them to rear quarter emblems - i know the door panel emblems are similar but these ones are quite thick and have long posts with speed nuts -  

price is 30.00 with 5.00 going to the site