1977 300d Help

Well, my old 300D, 365K miles, needs the starter replaced, for some reason, that bolt was the tightest one I have ever tried to remove, especially since it was in a very oily area on the car, I thought it would be easier. But nonetheless, after getting a hex socket, to remove the bolt it seems stripped. This is the lower bolt, there are also grips around the outside of these rounded bolts, they look a lot like the bolts that hold on the overhead cams, is there a tool that a mechanic can use to get a stripped one of these out, or does it have to be drilled etc. I would really appreciate some help, as the car has been sitting for a month while I sit here trying to figure out what to do with it.. Stumped, Jim