Don't know what year your Ranger is, but mine is a '92 and there are rubber grommets in the firewall which I was able to pass power leads into the cab and hook directly to the battery.
Rangers have issues with fuel pump noise, so be sure to add some ground straps from the cab and bed to the frame, and you might need to wrap the fuel pump leads in some ferrite toroidal cores like the snap on type.
If you need to run an antenna lead into the cab, there are usually some grommets in the cab floor near the rear of the cab.