your greatest gripping power is going to be with a pipe wrench with clean, sharp teeth in the jaws. by design, the pipe wrench wedges tighter with force, unlike a ViseGrip/pliers/etc. you'll be able to apply enough torque with a pipe wrench to snap that baby off so tap the end of the guide with a hammer while you are turning.

-dan

Also, old head bolts with heads ground off are *great* for keeping the head and gasket lined up as you install.

Having successfully replaced a 617 head and gasket (but hadn't thought of this), what an *outstanding* idea!