Pin weight you listed is dry, not loaded ready to camp. Expect a pin weight closer to 2500 pounds. Towing a fifth wheel is all about load carrying capacity, not towability. If you think you want to stick within the mfg GVWR as listed for the truck, you need to get some accurate weighs of the truck. The gas motor helps but I suspect you have a GVWR of 10,000 pounds and scale ready to travel around 8,000 pounds. You might have enough power, but I seriously doubt you will be happy. Your in MI, so your travel is relatively flat. Get into the mountains and all bets are off. Will 4.10s help? Not enough to be worth 2500 more dollars spent on your truck.