if you have plugged the holes in the firewall you could also think about going through the firewall down lower or the floor. that way there is less clutter under the hood. I have used something that looks like an extension cord to run the required wires to the rear on some industrial applications. it is smooth on the outside and has a fairly good neoprene rubber casing.it would be available from a trailer or trucking supply place.semi trucks have a 7 wire cord if required. I would run it to a sealed junction box at the rear and then branch out from there to the lights. I use the rubber coated bolt on clamps to tie the wire to the frame etc
https://www.grote.com/electrical-con...cable/82-5606/
https://www.cabletiesandmore.ca/cabl...insulated-zinc