70aarcuda is correct, I just checked with summit and MP.
W2 cylinder heads are no longer available in open chamber.
What kinda engine are you trying to build (street cruiser? occasional strip? torque monster? High rpm screamer? etc etc)
You might be able to get away with running camshaft with more duration and a wider lobe separation.
This cause the intake to close later, making your effective (or dynamic) compression ratio lower as compression doesn't really begin until both valves are closed.
OR if you only want to gain 2 or 3 cc's, a closed chamber head can easily be enlarged to suit your needs. You'd be surprised how quickly 3 cc's can be removed from alloy with the correct abrasive air-tools. for example, a mimimum-metal-removed polish of the chamber will usually be more than 1cc.
