Actually it's only 6 digits of the serial number that needs to match. According to [1] the game Michael Larson was trying to win was organized by $ale of the Century (SOTC), which was actually a TV show, not radio show. And as per [2] it was run for only 2 weeks in the fall of 1984, and the prize was indeed $30k as the Damn Interesting article claims. And there is a recording of an episode at [3] showing the six digits to match were "550085". Since Michael Larson had 100,000 bills, he basically had 10% chance of winning the $30k prize. If the game was run 14 times (over 2 weeks), he would have had a 77% chance of winning (1-.9^14)

I found another episode at [4] where the host even explains "according to the Treasury Department there as 3.7B one-dollar bills in circulation; that means [...] there are 3700 dollar bills with the winning number"

[1] https://www.gameshowforum.org/index.php?topic=5153.0

[2] https://tvtropes.org/pmwiki/pmwiki.php/Series/SaleOfTheCentu...

[3] https://www.youtube.com/watch?v=neCxKLjsow8&t=1510s

[4] https://www.youtube.com/watch?v=bnvSJZj3m0U&t=1296s