Or by looking at John's pictures, the starter location on a small block is below the center line of the bell (left side picture), and a big block trans has the starter location on the bell centerline (the bell on the right is a big block trans)'.
Just a side note, if the starter location is above the bell center line, it is a slant 6 trans (though the very early slant 6 727 used a small block trans and relocated the starter). Gene