Tacamo Towing Capacity

I have a 2002 V6 X-Cab 4x4. I really like the truck, it has been more than reliable and very capapble 4x4. I want to buy a boat in about a year (22'-25'). I am expecting the boats GTW to be anywhere from 4500 to 5500. The owners manual says 5,000 lbs is the max towing capacity. Is the towing capacity limited by the suspension? If so would some suspension mods increase the tacoma's capability. What suggestions, for modifactions, does anyone have to better equip my truck to do this heavy hauling...really trying to avoid buying another vehicle...this one is almost paid for.