https://www.hagerty.com/articles-vid...12_HagertyNews
"Fun fact: all 396 engines across the Chevy lineup were actually bored 0.30 over in 1969 due to lax emissions standards for engines over 400 cubic inches.
In the Chevelle, which had built an entire brand around the 396, Chevrolet kept this hush-hush, but in the pickups, where it was known by the L47 RPO code,
it was alternately labeled 396 or 400, confusing gear heads for decades afterwards."