just caught this thread so I'm late on answering but I like the responses.
I started off with the old-timers goal of 1hp per cubic inch. Having owned a 65' Mustang w/289, I always felt that 200hp seemed kinda lame for such a great looking car.
So when it came time to build my engine (I think everyone should do it at least once in their life), my short-block 347's goal was 347HP.
When I finally finished it and installed it into my FFR w/3.55 gears and T5 tranny out of a 91' Mustang, it produced 355 HP / 385 ft.-lbs. (4th gear pull). This was before the replacement of the Holley Street Avenger to a Barry Grant 650DP and Wilsons 1" spacer.
For the last 4 years, this engine has never failed to impress me. Very streetable, never overheats, never broke the drivetrain (using a T-Bird IRS) but I can only smoke the tires in 1st. It would be kinda neat to smoke them in 2nd too
But to be honest, I'd draw the limit at 500HP if I could afford to do one more engine (but have some pro do the work.) Time to start saving up.