Here's a site for heavy hitting 7M's:
http://www.7mpower.com/ I'm sure I've seen higher elsewhere though.
Highest power for what engine? 2JZ? 1JZ? 7M? 2JZ will get past 1000RWHP with a decent build up. I'm sure I've seen 7M's past 750 as well... don't know about the 1JZ.