Easy.
When you remove your dash pad, the sheetmetal under the pad already has holes through it for your mount. Worked like a champ in my buddies '86.
It'll be self explainatory when you remove the pad, then look at the bottom. I think all pads are made with provisions for it. Kinda like the handle you can put above your driver side. Cool stuff man. Jam a screwdriver through it and bolt in the mount. <img src="/forums/images/graemlins/kewl.gif" alt="" />

85 4Runner - With NEW Marlin 4.7 Gears!! It's a whole new beast!