well i would go with the 440 block over the 383 and stay under 680hp. the 383 looks weaker than the 440 botom end with the middle mains even smaller than the small older 440s.

i just took apart a nother 6630-440 block with .520 middle mains. those are real close to the good 400block thickness by .030 but not the hard to fine super block 440source talks about 400 wise anyway.

someone around my area says "my engine builder says" the 383 block is a stronger setup over a 440. well one would not know that just looking at it and mesuring things. and i am now gun shy since i split my 73 440 block.