Anecdotally, the story is told that the Fleer World Series 'update' cards (from 1971 and onward) were only available through Good Humor (I believe) ice cream trucks. People seem unsure if a single new card reflecting the previous fall's World Series was released each year or if all of them were put out together during the summer of '78(?).
Edited to add: This thread needs pics. Here's my Clemente...
1971fleerworldseries69.jpg