I cut a hole that was just big enough, half way up the B pillar just below the bump. This got covered with an ally plate, but you will have the luxury of welding it shut.
As well as the larger hole for the bolt a smaller hole or two will be needed to position the plate. From a previous post, MIG wire is great for this, you can then either weld the plate through the holes or pop-rivet.
I got the pre-made plates from a Trimmer/Seatbelt specialist which are galv plated too and only $3 a pop.
If you can't get them locally, I went to Willshire Motor Trimmers -
http://www.willshire.com.au/
