The drivers side bracket is a 383 mount that has been bent out and a short piece of angle iron is welded on. It bolts to the oil pump bosses that have been drilled and tapped. There would be no way to use a stock 383 mount on a 440 without the modifications, you would only be bolting it to one hole! Some 440 blocks have one boss on the front of the block but not all of them. Please take pictures of the block you have and the mount. To answer why not, the 440 block is 3/4" taller so the 383 mount would not work.
