I dont know where you got your block weights but they are wrong. A Gen III hemi block is waaaaaaay beefier than an LA block. Here is where people have provided weight comparisons..
http://www.protouringmopar.com/show...h-Weigh-anything-you-have-and-post-it-up-here I guess bottom line maybe the Hemi weighs as much as a small block with an aluminum intake? Apples to Oranges.
