Help needed - 1972 grill assembly pics needed

[Dukester]

First I want to say thank you....I am a Ford guy through and through but recently had a good buddy go through a stroke and isn't able to get out and work on his truck. I believe that I have everything to put a grill and headlight assembly on his 1972 C20. Everything is new but I can't figure out for the life of me what type of clips hold the outer aluminum shell to the plastic grill insert.

Both have square holes but the ones in the insert are slotted for adjustability.

Can someone please send me some step by step instructions so I can get my buddies rig together for when he is better.

Thanks!