Actually, there is some dispute between the PR3 (B16A) and the P72 (B18C1) heads. The P72 has smaller combustion chambers for higher compression, but the PR3 has higher overall flow ratings. The P72 head's flow is optimized for medium range revs while the PR3 is optimized for high revs. I remember seeing the flow graphs a while back.

I would advise sticking with the PR3 heads because they are compatible with B18C-R intake manifolds.

EDIT: The B17A uses a PR3 (standard B16A) head.