as copied from the 1998 GMPP catalog:
SBC PH 6 Aluminum Bow Tie Bare Head. (Discontinued). Listed on page 51 of GMPP 1998 catalog. The Phase 6 aluminum Bow Tie cylinder head (casting P/N 14011049) is the product of years of testing and development. The Phase 6 head has the highest performance potential of any Chevrolet cylinder head with standard intake port locations. It features high-flow intake runners, high-efficiency 55cc combustion chambers, and D-shaped exhaust ports. Port wall sections are extra thick to allow extensive modifications, and there are no water passages under the valve spring pockets. The spring pads are machined to accomodate standard length valve stems. The valve seat inserts are machined for 2.02" intake valves and 1.60" exhausts. The angled spark plug holes are machined for both tapered seat and gasketed plugs. Phase 6 heads are recommended for maximum effort racing engines which require a standard intake port location.
Technical Notes: Pushrod guideplates P/N 14011051 and 3/4" head bolt washers P/N 10051155 must be used with Phase 6 heads. Intake manifold P/N 10051102 is recommended for single four-barrel applications.
This is the same casting number but the chamber volume and exhaust port shape is different. Not sure if this helps you but it's info nonetheless.
BSE Racing Engines