400 stroker or 440
I'm glad someone posted a link to the "451 manifesto".
The advantages are:
slightly stronger
slightly lighter
slightly smaller
slightly more CID
all are small, but add up, and the big one-
more efficient.
That's why the Ford 302/5.0 (old, not new) was able to hang with and beat 350/5.7 GMs.
Contrary to popular belief, it's NOT all about displacement, although the 451 gives you that as well.
Don't get me wrong, I love 440s, but the 451 is just mathematically a better design.