yeah, very pointless swap... just throw the complete B20 in there... get a 99+ crv [or was it 98+ I forget] longblock and throw it in there... it'll be more fun than the gutless B16... the 96-98 B20 will be fun, but it's a little more gutless than the newer ones.
or you could throw the B16 head on the B20 block for some more fun
You can't put a B-series head on a K-series block they are designed very different and will not fit. Also why the K20A3? The performance isn't much better than a B16 and there are better K-series engines out there.