I have a 67 289 I don't know how similar they are. When I had to replace one of my freeze plugs this is how I remember doing it. I used a screw driver and placed it at the edge of the freeze plug and hit it with a hammer. This caused one side of the plug to go in toward the block and the other side came out. Its like flipping a coin. Then you can grab the part of the plug sticking out and pull it out. Obviously it will be a little more complicated if access to the plug is blocked by the engine mount.
I have used a tent puller/slide hammer. Just drill a hole in the plug. Thread the puller in and slide away. Not saying it doesnt work but I would worry about loosing one of those in the waterjackets doing the previous method... then again it would be just my luck anyways.
Kevin