Largest displacement of a factory 440 block?

451s can be made from factory castings in terms of rods, crank, and block. I've also heard of guys using factory type pistons, but I dont bother with the few pennies that might save. But in truth, if you dont already own a crank for this, it is a better choice to buy one. 440Source.com has a very nice performance crank, using B size mains, and stock rods, 3.75 stroke, with better material, and big radiuses, and the B size counterweight size (diameter) so it literally drops in a B block. When you add the cost of getting a crank core ($100-175 for a forged deal), magging it (to check for cracks..$75), have it turned down to B main size, turned and polished on the rods($200-300 around me), you are looking at spending $375-400+ on a factory used crank. And, you will need to clearance the block slightly to make it fit properly. That can be done by you, but it's still time and effort. Brandon sells them for $550. It's a much stronger piece, and aside form having the dimensions checked, it's ready to go. If you run heavier pistons, you may also need mallory metal to properly internal balance the assembly. Brandon's doesnt. The material and counterweight design is designed for this swap. Call it cheap insurance. He also offers complete kits, but they can be pricey IMO when comparing to available parts bought individually for this particular assembly.