You get more compression using an 848 head on a 261, but not 9:1. It's more like 8.3:1 unless you also deck the block.
You can also use a much more radical cam on a 261. 200 hp is pretty easy to get.
Also, you can build a Cadzilla 261 by using Cadillac pistons and rods and offset-grinding the crank to increse the stroke. Inliner's 12port news has an article on this.
