Its a pretty straight forward fix.
Take signal wire (~14 guage) from inside the cab that normally runs to the starter put it to positive side of coil input on relay.
Ground otherside of coil on relay (~same guage as starter wire)
Run wire from battery to high side of relay. (as heavy as you wish, 12 guage should be plenty)
Run wire from output side of relay to starter. (same as battery side of relay. Again 12 guage should be plenty)
The idea is that when key kicks on, it activates the coil, moving the relay, supplying full battery power from battery to starter.
~Nate
Here is a quick pic I drew from memory.
