Trying to decide on a LS9 block or an LSX. Will be using these as I can get them for cost at my dealership. (shipping to Canada is very high). Noticed the LS9 uses the same main caps as the lsx. Noticed it was also rated by GM for 900hp and the LS3 was rated at 550hp. So is it really that much stronger then the LS3? The 12mm headbolts wood be a plus as I only have 4 bolt heads. Never really hear of anyone using these, is there a reason for that?