ok here is my advice get a LS block for 100-150 and get it sleeved for around 700-1000. Because you figure a b20b/z is around 500 and the block gaurd is probably a hun so for 500 more you are sure that your motor won't blow up. if its the displacement you want it doesn't matter it you sleeve at 81mm or 84.5 mm it cost the same.