[FPB111]

Look at the pieces listed on the Pelican page.
LOOK AT THIS PAGE ON PELICAN,
http://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2016.cgi?command=show_part_page&please_wait=NG&make=POR&model=927&section=BDYEXT&page=3&bookmark=8&part_number=PEL-996-BRACKET

TWO SPACERS, LEFT AND RIGHT, TWO SQUARE LOCKING NUTS.
ON THIS PAGE LISTED BELOW

http://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2016.cgi?command=show_part_page&please_wait=NG&make=POR&model=927&section=BDYEXT&page=3&bookmark=8&part_number=PEL-996-BRACKET

LOOK AT THE PAGE REFERENCED ABOVE.

Everything mounts from the front.
My C2 holes were enlarged by a PO so I used these plastic Twist Lock anchors with the stock spacers and plate mount. Never came off.
http://www.homedepot.com/p/E-Z-Ancor-Twist-N-Lock-75-lb-8-x-1-1-4-in-Philips-Zinc-Plated-Nylon-Flat-Head-Drywall-Anchors-with-Screws-4-Pack-11364/100165900