I just picked up a '42 block with a bad crank, I bought it for a spare block for my '37. So the question is now, will my '37 crank fit? There is some differences in the rear seal area right? I also see that this block has a "draft tube" cast into the rear of the block. Can I still use my '37 valley covers and just ignore this passage in the rear of the '42 block? Any other differences that make a difference?