I attached mine to the side of the stearing column support bracket with double sided adheasive tape. The bracket has a flat area on the left side that was large enough for my amplifier box, the bracket looks like it is aluminum.
By the way, I was able to thread the wires up the pillar using a stiff wire inserted from above to pull the wires up from below the dash. I routed the wires and boost tubing for my 3 pillar gauges this way. Also, you can get power from the fuse block. I used an "Add-a-circuit" that lets you piggy-back a new circuit onto one of your lightly loaded circuits. You do have to modify the "Add-a circuit" plug-in slightly with a file to fit the fuse slot. Compare the "plug-in" with a fuse and you should be able to see what needs to be modified. I got the 'Add-a-circuits" at Auto Zone. Hope this is of some help to you.
Dick