Looking at the pics in the parts books, and the pic posted above, it looks like the mounting bosses (through which the vertical mounting screws go) on the 69 box would place the fuses in the vertical. I think that the mounting bosses on the 79 box are at 90 degrees to those on the 69 box hence the 79 box would have the fuses in the horizontal position.
Just going by what they look like in the parts books so I can't say for certain.