I can't recall ever seeing one on a /6 early A, but I have seen several of the sheet metal fan shrouds that were exactly as you described. The dang shrouds weighed as much as the radiator!
I think I am going to either make one, or modify one. No over heating at all, but I am getting ready to swap to a better fan and smaller water pump pulley "just because" I have them and I thought I might add a shroud, too.
