I do belive BB motor mounts are diffrent than SB mounts. Don't worry though there is plenty of room for a BBC under the hood.
The rub motor mount is the same on 4.1 straight 6 but the motor mount bracket is different. The small block clam shell is the same for big block on most vehicles depending on frame you might have to use the set up for the big block or 305 or 350 motor mount brackets.