I did this already. To do so, run a 16awg wire pair from inside the cabin where your switch is mounted through the firewall. I route my wires through the diamond shaped plate where the clutch cylinder would have been attached. Run the wires (inside a wire loom for protection) along the cowl beside the brake lines and down to the fuse box behind the battery.
First, pop out the fuel pump fuse. Turn the ignition to ON and using a voltmeter, check which one of the fuse terminals is hot. The non-hot side goes to the fuel pump. You will be cutting the wire on that side of the fuse later. Turn off the ignition and replace the fuse.
Unbolt the fuse box. Remove the alternator wire from the stud on the fuse box. You may also need to remove the positive battery cable to give you more room to work on the fuse box. Use small flat screwdrivers to pop open the clips holding the upper and lower halves of the fuse box together. Locate the fuel pump fuse. Cut the FP fuse wire you identified earlier and connect the ends of your switch wires to the the cut wire. You should use male/female solderless connectors on the OEM cut wire in case you want to undo the mod later. Route your wires along the existing wire bundle, then snap the top and bottom halves together. Put it al back together and you’re done!