The difference being a 426 wedge is just a 440 with a smaller bore. The 426 wedge and the 426 hemi do share the same bore/stroke, take the same crank dimensions, etc. So you COULD put a set of 426 hemi pistons into a 426 wedge block and you COULD put a 426 hemi cam into a 426 wedge block. However that would all be useless because you can't put the 426 hemi heads on the 426 wedge block. The Hemi block has holes cast in the block where the exhaust pushrods go through. In a hemi, the exhaust pushrods come up through the block deck, through the coolant jacket, go through the head gasket, etc where on a wedge they don't. The top row of head bolts is also different, with the Hemi having the top row located further up, in an area not cast into a wedge block. Hemis also had oil drains cast into the block at each outer corner of the cylinder head mounting face, this area is not there on a wedge block. There was a company (stage v) that used to make Hemi heads to fit the wedge block, but with the availability of aftermarket hemi blocks, nobody really has a need for them these days.

Then of course hemis had cross bolted main caps, two bolts going up the bottom like a wedge, but also two bolts doing in from the side of the block.