These pins are necessary to correctly align the head on the block.
If the pins are unable to be grasped with vice grips, I would drill them and tap the pins and use a bolt to extract the remaining shell...
The pins measure 0.316" in diameter so you should be able to drill them with a 3/16" drill and tap 1/4" ...this should give you enough bite to remove the pin remains.
The pins are only 0.629" long so don't drill too deep.
Replacement pins are readily available from most suppliers.
