Appears to be a 12 port engine:
Ex-In-In-Ex-In-Ex-Ex-In-Ex-In-In-Ex
3.30" X 4.40".
Many excellent exploded diagrams: http://tinyurl.com/qql2ka5

The same techniques apply here as for any SV engine: minimize piston to head clearance, more CR, split exhaust, cam regrind, larger intake valves, relieve the block deck.