My bumpers are after market, but still use the 4 on each side bolt holes...If I recall correctly, on the stocker , you need to remove the bumper, then the brackets...
The jcr add looks like its for a pair...and only use 4 bolts per side...the ones I have fromorris, use 5 bolts per side...if you look at both adds, you will see the Morris on has one for a bolt the hole on the outside lip on the back bumper area.