The manual has been indexed:
http://67-72chevytrucks.com/vboard/s...d.php?t=563097
Download the spreadsheet here. Looks like page 426, of you have a digital copy it should be numbered but paper copies don't have page numbers.
I believe the bottom uses existing bedside to floor bolt holes. Then you drill where the top lands on the bed side flange. That's how mine was anyway on a 67 SWB.