Correct me if I'm wrong, but the L98 aluminum vette head and the zz4 head are identical. Would this mean if I was to bolt on some zz4 heads, my car would still be street legal and pass emissions. In other words, there would be no difference between the two heads.

so long as your car is a corvette yes. if it's a thirdgen then no. the aluminum heads do not have egr passages in them. you can make them legal by getting the egr system from the corvette.