Did you look in this forum's library? Try topic "Mustang Hardware Spreadsheet 67-68". There are two files, one by application (use), the other by part number. All entries have the source referenced.
Jim
I did check both spreadsheets. 380503-S8 is listed as GAS PEDAL-ACCELERATOR ARM but interesting it's only listed for year 67, 68 column is not marked. The finish is of course S8.
And in the AMK Ford fasteners guide page 139 380503 is listed with just S finish so I'm not sure what exact finish from that entry.
I do have 2 screws now, the first from NPD and the second from Magic Valley Mustang. The second one is a Scott Drake part and it's P&O so I'll remove the P&O from that one.
PS One other note. Apparently as of April 25, 1968, the pin screw changed. I've seen C8OZ-9873-1A being listed and it's a silver pin that looks very different from the one I have. I've attached a picture from NPD.