I think what he means is that the B18C1 head has a smaller combustion chamber then the B16a, therefore using the B16A head on the B18C1 block will slightly lower compression.
B16A head + B18C1 block = poor man's type R <---search for this.
If keeping the B18C1 head, I don't know if the Type R IM will bolt up to it, but the Skunk2 IM are similar and will bolt up. The point of using the B16 head is that it flows better then the B18C1 head which means more HP, the slight drop in compression won't matter as much, since its static compression, as how the head flows. I believe the B16 and Type R heads are the same casting.