The front doors are prewired for speakers in the door to make it a 6 speaker system (must have been an option). To make the speakers work in the front doors you need speaker (6.5 inch) and an amp from either a 240 or a 740 that had the 6 speaker system, the 240 even though the same is easier to find and probably cheaper. The 4 channel amp just plugs into the same hareness and the same way the 2 channel does, even bolts in the same way once the 2ch is removed. I am going to work on pictures for this, I'll keep you posted.