I hope you mean cableS.
There are several unused grommets in the firewall of Dodge trucks. Plus, there is an unused teat on the main wiring harness grommet. You just need to be careful not to interfere with existing wiring.
PS: I guess you got a good deal too. The local Dodge dealer here has been selling 3500 diesel 4 door, extended bed models for $15,000 discount off the door sticker.