I don't know how long these have been out, but came across one of these hoods the other night. From Goodmark industries I believe.
They seem to have them listed for 79/80 trucks, probably catering to the Little red express guys. But regardless brand new birdbath hoods is a good thing!
Numbers I've found it listed under.....
4271426
CH1230200
Or you can go to E-bay auction # 151448391785