Did a dry fit to try to work it out for myself. Don’t remember the ‘extra’ hole at the bottom of the triangle bracket, but this is the only way it goes together that makes sense.
IF the triangular bracket IS the alternator bracket and not for the PS then 2 of the holes would be bolted to the WP bolts, and the alternator would be moved forward so the front ear is in front of the top hole of the triangular bracket. the photos below are from 67 273 with cast iron WP BUT my bet is they did not change things all that much through the years.
(note: in this photo I had the adjusting bracket in the wrong location)