396 Cam change for 1971

[davepl]

And yes, I know it was the 402. But I was doing some research yesterday on what cams actually came in the 396s, and noticed that as of 1971 they added more exhaust lift and duration (still a very mild cam).

I'm wondering what this might have coincided with, like a switch to open port cylinder heads perhaps?

Curious as to what else in the motor changed for '71 that would have necessitated a cam change, or if it was "just because".