I think it is interesting to compare how a new truck compared to your 09 f450:
In order to get your rig moving your 450 with a 4.30 rear axle ratio was able to theoretically put almost 8700 lb ft of torque to its rear axle in low gear.(rear axle ratio of 4.3 x low gear ratio of 3.11 x max engine torque of 650)
A new f350 with a 3.55 rear axle can put 13000 lb ft of torque to the rear axle. (3.55 x 3.974 x 925)
I think it is also important to consider that your toy hauler has 3 axles.....with 3 axles there isn't as much weight that needs to be carried on the pin. Additionally 3 axles tend to tow very nice and straight especially when your rv is 40 ft long.