I had my block heater blow out last year on my 350. I replaced it with a freeze plug but wasn't able to get anything in there to knock it in. I ended up having to unbolt the exhaust from the manifold and cutting it at the straight part under the oil pan. With that out of the way I just used a big socket and tapped in the freeze plug. I reinstalled the exhaust by using a sleeve and clamps on the part that I cut. I would suggest replacing the heat shield (you'll have to remove it with the exhaust) or using something else (maybe wrap). It looks like the exhaust heat has dried out my rear seal. Oh, and be careful tapping in that freeze plug. It's easy to go too far and push it into the block.
Ya I know how to put the freeze plugs in. I put These ones in when I rebuilt the engine. But as it turns out the machine shop gave me the wrong size freeze plugs. What I need to know Is if there's any way to get up behind the engine mount to put that particular one in or how I should go about it. It's the freeze plug on the driver side under the engine mount. I believe 2nd from the rear of the block.