Head, singular. Honda guys only get one.

The B16A head really won't change the compression ratio, but if you reenforce the bottom end a bit to allow it to rev safely, horsepower will jump nicely with the addition of VTEC present in the 1.6l B16A head. Other mods are required to even get it on though.

Mind you, the B20Z uses a head that came out in '89 as a 90 model in the Acura Integra (B18A). It's based on the ZC head which came out around '84 in Japan, '85 (as an 86 model) in the US. It's not that new.