For trucks south of the 49th, it may be fine to just add relays and a new wiring harness and use the stock wiring to trigger them. Canadian spec. trucks have a DRL module which puts out 50% power to the high beams by turning them on and off really fast. (not sure of the actual frequency, but it would be in 100s of Hz)You cannot use this to trigger a relay. If the stock wiring causes too much of a voltage drop, then putting in higher wattage bulbs will only make matters worse. The easiest way to get more light is to install bulbs with the same power rating, but more efficient, thus more light.
Jim