I ran a hose for my boost guage through the firewall, right below the brake booster. Not much point in giving you specifics, since my steering wheel is on the right, but just use something that goes through already as a point of reference, so you don't go through anything important with your drill bit. Don't forget to put a rubber grommet around the hole too, so the wire doesn't end up shorting on the sheetmetal.

But if only wires, I'd go with JB and use an existing, via coathanger. The main loom goes through there, and there's always room for a few more... <img src="/forums/images/graemlins/cyclops.gif" alt="" />