A good rule of thumb for a daily driver is 1 HP per cubic inch. Any thing more and you are talking big bucks to make it suitable to drive on the street. If you want the performance of a 400 cubic inch, then you need to get a 400 cubic inch motor. Having said all this, if you do not have the "power pack", the Rochester 4 barrel set up will not make much difference except in sound and reduced fuel milage. Get bigger valve heads and a moderate cam to go with it and you will see some increased preformance.