Just a little info for the curious on B-series intake manifolds:

There are at least three different intake manifold bolt patterns for B-series engines, since there are at least four different variations of B-series cylinder head.

1) PR3/P73 head: B16A, B17A, B16B, B18C (Type-R), B18C3/5
2) PR4 head: B18A/B, B20B/Z
3) P72 head: B18C (SiR-G), B18C1

The B20A/B21A probably also used a different manifold, but I have no confrirmation nor do I know the head casting code. I do know that the head itself is vastly different from any other B-series, so a different manifold bolt pattern would make sense.

Exhaust manifold bolt patterns are identical for PR3/P73, PR4, and P72 type heads. Go figure. The B20A/B21A, once again I don't know.