NHRA went to 500 in. engines in 1982. Destroked 396 Hemis were popular, but John Hagen was making news by setting the MPH record with a low deck big block modified to accept Hemi heads before that. Charlie Malyuke was behind the mod. Don't know off hand how small they went with that.
I believe Paul Gentilozzi got Gliddens Arrow and parts after he went back to Ford.
With a pound-per-cubic inch format, a smaller engine is more efficient. In other words, it's usually easier to make more HP per cubic inch.
