first generation rivieras had flat spokes. i had a set and what also set them apart was that the angles are smoother on the spokes. mine were raw/sandcast but these could be polished some time.
the guy (nico86) i sold them to still has them on his car i believe. he will post as he is still quite active here
Yes, still have those wheels on my car
Angles are smoother indeed, and they compared to the wheel pictured on the first post of this thread they don't have this casting around the center. And they have the thin lip without this safety lip for the tire.
Will post a pic later when I'm on my laptop.