I always try to use the upper and lower bolts. Try rotatong the mountomg plate 180 degrees and seeing if the arms will reach. Thats a heavy engone and you dont want it balancing in the air and held up by only the bottom. you want a good center of gravity, not only for safety but for ease of movement. You have to roll the engine over to get to all angles of it. Seeing as bbc and sbc have the same bell housing pattern, I would assume it wont be too much of an issue to do. And about a half inch of bolt on each bolt should hold. You dont want to bottom it out, but you dont want it barely clinging.