I have 440's and a couple 400's and I have researched and if you would have asked me 10 years ago I would have said 440 but knowing what I do know about 400's and Strokers It is definately 400 for me, I just dropped off a 72 400 block and a 72 440 steel crank to my machinist to hot tank and start on my journey to 451 Stroker land! Shorter deck equals stronger more rigid block, less height less flex, 400 has the biggest bore of ANY big block Mopar, so as much as I love saying "440" I will have to say 400 block!