Just because the part numbers vary does not mean that they are not essentially the same block. There are very few differences between the 2JZGTE and the 2JZGE engines for toyota, but they are definatley different part numbers and different outputs, just for example. If the LS7 was so different, it wouldn't be an LS. As far as LS1 to LS6 the main difference from what I understand is the oil system as far as the galleys are concerned for 2 of the cylinders. The LS2 is a 6L instead of a 5.7L and the LS3 is a 6.2 or 6.3 if I remember correctly. The LS9 is basically a supercharged LS3 and the LS7 is the new 427 505hp that comes in the new Z06.
