the pump should be mounted in its orignal aspect as on the orignal car idealy but as long as you mount it as low as possible to the hight of the pickup in the tank inlet to the bottom . inertnal pumps are mounted upright due to the pickup strainer siting on the bottom of the tank.
as for the cable i would run a single cable of simular size (2.5 mm would be fine) you dont want voltage or the eletric leaking out as smoke
when i build my chassis im thinking of running a length of copex down the trans tunnel to get all the cables in so its possible to draw a new cable in
