No, ALL 400s are beefier than any other factory big block besides the Hemi w/cross bolted mains. Beyond that, there are some cold weather blocks, cast between early 71 and mid '71 (thru June I think) whose casting number ends in "230" that have even thicker main webbing. If you have a 383 or 440 next to a 400 you'll see why they are stronger...
