Hi Vince
If you put a 4.25 crank in a 454 block u have to run a longer rod, a 6.385 and then get the pistons for those rods which will have relocated pins.
The 496 is a 60 over 1/4 stroked 454 and is most popular and easier to get parts for than some of the other combos.
I am building my current motor based on those configurations.
Its only use will be at the strip I will looking at in the neighborhood of 700 to 800 horses, these engines make a good choice for street cars though because of the monster torque they make, I'd say with flat tops and some good heads and cam carb combo you can be looking 5 and 5 for the street easy. Build a stout bottem end and dont go cheap, these engines require good parts to live. If you want more specific info on parts for a good combo just reply and tell us your car specs and intended use. Goodluck, Charles