You can remove all the wiring on the passenger's side of the engine compartment. If you're planning to run electrical gauges, you can use the existing wiring that is for the factory gauges/idiot lights, but it probably wouldn't be a bad idea to run new wiring for them. If not, it's kind of like running an old, used fuel filter with a new fuel system. It may work, but probably wouldn't give optimum performance.
Are you planning on running lights, etc.? A good place to start is to get a manual with wiring diagrams for the car. I haven't cut anything at the bulkhead near the brake booster, but everything on the passegner's side is gone.
It really depends on what you are really planning to wire with the car. If you're sticking with the column switch, turn signals, etc., I would leave everything on the driver's side alone.