I would use good quality stranded wire, 18ga or bigger, and tuck it away to be as hidden as possible. Be sure to leave moderate extra length for flexing but secure the harness from excessive movement and make sure no wires can get into the moving parts.
I'd try to use as many LED lamps as possible, to keep power requirements down. I'd use an H4 type headlight. It's pretty easy to find LED lamps in H4, 1156, 1157, B9s, and T10 sizes, so original fixtures can be retained, unless you prefer the styling of the new chinese stuff.