Another in the news last year was a newer Silverado ('96/97, I think?) that an older farmer had put 1,000,000 miles on and the bigger part of the story was he was the first to put all those miles on a single K&N Filter, to meet their 1,000,000 mile warranty. K&N rewarded him with a new Silverado.
But yeah, not at all uncommon.
For more examples, here's a site GM started a while back:
They started it as a "200k" club, but clearly most were there or well beyond that...and with interesting stories. Most are easily on original engines, many still have original transmissions, and most also claim just basic maintenance...from our experience with GM vehicles, especially trucks & BOF, RWD cars, that's very normal.