1970 - East Tennessee 200 at Smoky Mountain Raceway in Maryville, TN
http://bench-racing.blogspot.com/2012/07/july-24-this-day-in-petty-history-part-1.html
1971 - Nashville 420 at Nashville Fairgrounds Speedway
http://bench-racing.blogspot.com/2012/07/july-24-this-day-in-petty-history-part-2.html
Chase, a page 6 article from the July 24, 1970 Kingsport Times does refer to a makeup race date at Smoky Mountain as you presume. I did not pay to open the archive. Just noted it in a Google search.
http://newspaperarchive.com/kingsport-times/1970-07-24/page-6/
I updated my blog posts for King Richard's two Tennessee wins on July 24th in back-to-back years. The links above are still relevant.
For the 1970 race at Maryville, I found this really neat column by Buddy Chapman of Hendersonville NC's Times-News. He spent time just hanging out with several of the drivers and crewmen on Thursday July 23rd when the race was rained out as they relaxed and waited to race.
With the race rescheduled for Friday night July 24th, the teams had to immediately leave for Nashville to make a 9AM qualifying session and 2:30 PM start for the Nashville 420! Talk about no rest for the weary. Source: The Tennessean
Lee Roy Yarbrough skipped the Maryville race to help promo the Nashville race.
A couple of new nuggets for the 1971 Nashville 420 win by Petty
James Hylton drew a tough assignment to help promo the race.
Ed Negre relaxing a bit before the 420
The Petty crew services the 43 Plymouth
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