Conversation so far:
When was the National 500 held?
The 1973 National 500 was held October 7, 1973.
Did Bobby do well in the race?
The first three cars to cross the finish line after the scheduled 334 laps (501 miles) were driven by Cale Yarborough, Richard Petty, and Bobby Allison.
What happened after the race?
What is disputed, is the legality of the first two cars' engines.

Question: Why was there a dispute?
Self-contained rewrite: Why was there a dispute regarding the legality of the first two cars' engines in the 1973 National 500?