I just finished up a 451" with a lunati hyd roller Mopar stage 6 heads mated to a 4L60 and am getting 17 MPG ( US gallons)
Using a quickfuel 850 carb, Dana 3:55 rear end
cam card.... http://www.lunatipower.com/CamSpec.aspx?p=60312

Power output? Don't know never dyno'ed it? 540 or so I'd guess? Engine builder figures closer to 600? Don't know , don't care. It's more motor than the tires can handle anyhow!
Just a street car, not a drag racer.
More info on the engine build... http://www.cuda-challenger.com/cc/index.php?topic=78386.0

I like my cake... and eating it too!