Remove any material "swaged" over them. Drill a small hole in them, and pull them out with a drywall or wood screw. It helps to heat the material around them for about 15 seconds with a propane torch. In most cases they just about fall out.
Pressure test the front plugs as well. Had a later 70's Chevy carb in here yesterday and the front plugs looked fine, but were leaking like Niagra Falls when we pressure tested them.....Cliff