The mains are a different size, so, the way to destroke a big block is with a custom crank, starting with a forged steel crank, not the nodular crank. Essentiailly the crank shop can then reweld the rod journals (you want to keep the RB main journals), and the stroke on the rod journals is then shortened. From there it is a matter of determining how short a stroke you want, use the stock 440 length rods and custom pistons with the piston pin located lower on the piston.
Now, the thing is, shortening the stroke on a 440 isn't that great an idea, the piston diameter is pretty large, so the B block 361 will give you a 4.125 inch bore, which is a great winding engine and except for the pistons themselves, is a 383 (4.250 bore) or a 400 (4.340 inch bore, which is larger than the 440 bore at 4.320), which is way large in the filling and burning in the shorter stroke engine, so take that into consideration if building this engine.
As a side note, the 361 is a truly awesome capable engine, and the older closed chamber heads keep the compression up in the 9:1 very easily, and the aftermarket Edelbrock aluminum heads can fit the 2.18 intakes within the bore easily for even more fun.
