In all honesty, you could probubly get close to that magical 1000hp out of the 3.7 v6. Now, I'm not saying thAt you or I could do that, but a professional speed shop or team with all the knowledge and top of the line equipment could probably bore and sleeve that bad boy plus a slew of other mods and get some crazy numbers. Now, I know that's not practical but if the question here is how much can you get out if your v6 then the sky is the limit... If you have the pocket book to fund it that is.
"Turn the mic back on" -Winston Churchill