I was in the same boat this time last year, dually or single rear wheel. I knew I would be close to max with a single rear wheel truck, but I just couldn't pull the trigger on a dually. Overall I am happy with my purchase of a 2017 3500 Duramax towing a 310GK. I have a 60 gallon aux fuel tank in the bed and just added a Onan 5.5 diesel generator in front of the fifth wheel hitch. I scaled my truck yesterday with 1/2 tank of fuel in my aux tank and full tank of fuel in the truck. 5480 lbs front axle and 4000 rear axle with no passengers. I might try to scale my truck with the trailer hooked up today to see where I am at. So I have an extra 800 lbs in the bed of my truck and I am almost maxxed out, I can always reduce how much fuel I am carrying and alter the storage in the 5er to keep weight off of the pin.