From a post above:
F072IJC
F = Flint, MI
07 = July
21 = 21st
JC = 3100-4000 series truck with RPO-227 (11" heavy-duty clutch? maybe someone can confirm that RPO # and what it refers to)?
The cam timing gear in a truck engine was metal (composite material timing gear was use in in a car engine). I think those cam gears were interchangeable - the composite gear was quieter and the metal gear was stronger/longer-wearing (but noisier)
