its a great idea to install a sealed junction box at the rear and run a cable, like a sheathed cord that has multiple conductors, from front to rear. a lot of trailer supply places sell the electrical cord style with the correct colors inside to match automotive electrical coloring. this makes it easy to run, easy to clamp to the frame with frame clips and also works pretty well for standing up to mechanical damage. in the past I have also run multiple single conductor wires through Synflex tubing, like air brake tubing, and used compression fittings at junction boxes etc. this stands up to mechanical damage better, IE: 4x4 trucks or off road equipment. the Synflex is also available in different colors if you like to coordinate. most electrical supply places could help you out with some good quality multi conductor, flexible sheathed cord if you wanted to go with whatever color on the strands. check the ratings for what the cord is made to withstand, heat, cold, wet, dry etc.
here is an overkill example of a sealed junction box. they do make them smaller. note compression fittings on the cording. wouldn't that look purdy.
https://www.bing.com/images/search?v...jaxhist=0&vt=0