Here is what I found for the 24 cards in Series #14 so far. It looks like the first print run has no letter. I've only found those from Italy. Is there a first print run from Japan? In addition, I am finding print run "A" and print run "B". So I'm working on getting all three versions for Series #14.
I have every card from print run 'A' and I am only missing one card (#09) from the first print run. For print run "B" I am missing #03, #09, #11, #12 and #18.
Here are the back variations I've seen. I have yet to check for variations on the front of the cards.
14-06 Kayaking - 'A' and 'B' have different text
14-07 Motorcycle Racing 500 cc WCH - 'A' has 1978 update; 'B' has 1979 update
14-08 Victor Saneev Track and Field - 'A' and 'B' have different subtitles
14-21 Heini Hemmi Alpine Skiing - 'A' and 'B' have updated records
03 - George Foreman
09 - Oakland A's
11 - Maury Wills
12 - Emil Zatopek
18 - Oscar Robertson
I was surprised to see that I am missing Zatopek's other versions since I have lots of his cards since I've purchased numerous of track and field lots.