Here is the info I collected from the other site, mostly based on 84-86 Mustangs.
-Ford Number 388664-S100
-Auveco number is 14127
-http://www.clipsandfasteners.com/Fascia_Bumper_Rivet_3_16_Dia_3_8_1_2_Grip_Ford_p/a14127.htm
-9/16 flange, likely can get these at a local auto body supply
I was lead to believe the Auveco replacements had the raised ring. Have you verified they do not?