I have a 2" BL...I raised a Shrockworks bumper, not an ARB though.
To raise the bumper I drilled new mounting holes in the frame horns, and used the bumper's existing mount holes to attach at the lifted location.
All you have to do is make the holes 2" higher than the original holes to have no gap...I chose to leave about 3/4" for flex room....so I didn't raise mine all the way.
If you don't have a winch in your ARB, I think that's all you need to do.
I know you wanted details, but its just pretty simple really...
Take off the bumper, drill a new hole in the frame horn directly above each original hole...
Put the bumper back on using the new holes instead of the old ones.
I have a 9,500 lb cap winch mounted in the bumper, so I didn't want to torque the frame on off angle pulls...So I welded L brackets on top of the horns, and bolted the bumper's original end of frame horn bolts into the L's.
I then welded a cross brace between the horns, making a V intersecting at the frame cross member.
Seems rock solid now....much stronger than stock.
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- TJ
2001 Xterra '03 VG33, SE 5 spd, 305/70/16's, Revolvers, UBSkidderz, Doubled AAL's, 3"SL/2"BL, winch/bumpers, skids, sliders, OBA, Snorkel, pine stripes....
Friends don't let friends drive stock.
http://www.gifsoup.com/view/501230/tj-tackling-crawlers-ridge-o.gif