It can depend on what you plan to use the car for. For all out racing car the 400 is the strongest in the crank webbing area and the 400 has the largest bore so many like to use it. For a street car that may get raced every now and then like I do the 440 should hold up fine up to about 650 hp. I use the 440 block for my 493 build and one reason was also because the 440 raised block has a better intake selection also and I knew most of the time my car is just street driven and not run hard. Mine is around 600 flywheel hp and its been in my car since 2011 with no problems at all. You just need to weigh out your options of how you plan to use the car as the 440 will hold up fine up to so much hp (around 650) but over that the stronger 400 is the better choice as long as it takes the intake you plan to use. Ron