There a lot of different ways to get a 13 ram 1500 give me more info and it will help us further.
6spd or 8
Air suspension?
Gears? 3.21 3.55 or 3.92. You say 10,000 lbs towing but not many actually select the 3.92 rear axle ratio. Also there is a huge ongoing issue as many 13 rams came equipped with the wrong axle which reduced trailering abilities. I would recommend getting under the truck and looking for a white sticker with the numbers mentioned before as not many know about it.
Payload of 1245 is from yellow sticker correct? I've seen payload of 894 on a longhorn, I know you have a Laramie but that is also a very well equipped truck with a reduced payload.