Mike:
I knew nothing about that game or backstory. Thanks for sharing your pennant and supporting article.
It sure seems to be a legit pennant made for sale at this historic "Soul Bowl" game. The pennant's by WGN; and, they used this same artwork + letter font to commemorate Super Bowl pennants made during the late 1960s and early 1970s. Special event pennants were kind of their jam. Since an estimated 60,000 fans packed Yankee Stadium to watch this game, I have little doubt the company viewed a game of this caliber as being pennant-worthy.
In fact, there's a 1968 Super Bowl II dueling pennant by WGN showcasing the Packers vs. Raiders matchup from that year's game. It had to have been made a few weeks away from this game. It looks quite similar to yours; same artwork; same letter script, except it reads, "Super Bowl" rather than "Soul Bowl." See:
https://pennantfever.weebly.com/blog...ry/wgn-flag-co
Again, thanks for the history lesson. This is why I love pennants!