under the vehicle is your best option unless you dont care if it is visible or you plan on ripping the whole interior out to make room for the 10 dif runs inside the vehicle
it will be for dd and comps and i concidered running them under the car beside the frame but im not sure how and i would rather run them inside but i dont know where to go throught the firewall to get them inside the vehicle
its easiest to run them under. for that many wires i would get like this material like a fire hose thats very strong and heat resistant and then just put all the wires in that and run that down.