My 1966 with a 283 has an original fan shroud, and is made of fiberglass. I have owned two 1966 trucks that had the inline 6, and both did not have fan shrouds. I never had any cooling problems with either of those 6 cylinder engines.
Brad,
Let me know if you need a picture of the fan shroud in my 1966 C-10. I can take a picture, and e-mail it to you.
