So far, I've been able to come up with three aluminum 5.3L engines, the LC9, LH6 and L76. I was told the L33 is an all aluminum 5.3 also, but haven't been able to confirm. Looks like the only 4.8L all aluminum engine is the LY2.
These engiens are just too big a PITA, I'm going gen 1 or 2 iron block aluminum heads for now.