I am going to be getting my dad's old Cummins. It is an 03 Regular Cab Automatic. I go 4 wheeler riding a lot and I was wondering how well it would tow a trailer with 5 quads. Also, our 20 foot boat might be pulled by this truck. Is there anything I need to do to the truck for this kind of towing?

Shouldnt have to do anything for those trailers. You probably wont even know they are back there :D