[ZeGermanHam]

For a street cruiser, there is absolutely nothing wrong with using a 557 block. With that said, good standard bore non-557 400ci blocks can still be found for $500 fairly easily. If it were me, since you're going through the trouble of building a new engine from the ground up, I'd pay the few hundred extra dollars to get an earlier 400ci block that will give you the freedom to increase power if you ever want to down the road.