One of the first things I did when I bought the BT-50 was to install the a Tekonsha Prodigy electric brake controller. from the Pajero. It is fitted into the centre of the console.
The cable loom was reused and all power cables and the cables to the trailer were good 6mm auto cable. The trailer wire was run out through the body behind the rear seat on the right hand side. A grommet was used. An auto-resetting circuit breaker was used on the +12v power line from the battery.