The upper right in the picture is the driver's side motor mount. It bolts on to the two holes in the oil pump flange and the front ear on the side of the block. Some B-RB blocks have the bosses but not drilled and tapped and some don't even have the bosses. Some C-body cars used the same set up and that's how I got a 440 for a good 361 and a $125 back in the day.