Ok, let's rewind this exercise.
I should have done a bit moire homework before asking. After noting that the 6 cyl and 8 cyl manual transmissions use the same bolt I should have checked the Fastener Spreadsheet to check for other places this bolt was used.
From the spreadsheet it lists:
Qty FIN :: Text :: Yrs
4 :: -S8 :: ENGINE MOUNT,FR,INSULATOR-ENG SUPPORT BRACKET,200 I6 :: 67 & 68
2 :: -S2 :: ENGINE MOUNT,REAR,MOUNT-TRANS,MT,289 :: 67
2 :: -S2 :: ENGINE MOUNT,REAR,MOUNT-TRANS,MT,289&302 :: 68
2 :: -S8 :: ENGINE MOUNT,REAR,MOUNT-TRANS,MT,289&302 :: 68
I next looked in the "AMK Products Guide to Ford Fasteners" for the 359080 fastener and the pic (below) shows a circled E with 4 radials at 90 deg. Although this doesn't match my pic with 3 radials it does lead me to believe the circle E style may well be correct. It's believed the radials denote the hardness of the fastener.