13k is no sweat for a GN. My deere weighs in somewhere around 10k with the loader, and loaded tires. I'd be looking for a 16k minimum and more likely a 20k GN. Length would be a minimum of the rig length plus 5'. If you pull the tractor on first, you are going to have ALOT of pin weight. I wouldn't be surprised if you had to haul this setup backwards.