With the mast laying on wood horses you can remove the masthead cap and use a fish-tape to pull the wire. If you have conduit inside the mast it will be exposed and you will be able to take advantage of that. If you don't have conduit, you may want to add it, or use cable-ties on the wire every few feet (with ends left long) to keep the wires from slapping the inside of the mast as the boat rocks. With mast on the ground you will also be able to make a more "workman-like" job of attaching your instruments and running the wire. Make sure you don't leave sharp edges on holes that will chafe through insulation and cause an electrical short. It's a good idea to use rubber grommets to line holes, or put extra wraps of tape to protect insulation where wires exit the mast.

If you can't unstep the mast, a temporary measure might be to run the wires along one of the top shrouds or jumper stays secured with tape every few feet. Then you can re-wire and do the job right when you can drop the mast.