I towed with ford e series vans from 1976 - 2003. 2003 -present I have a Chevy express. Vans tow differently than pick-ups. Wind/air displacement, center of gravity, inertia, are all different. Vans are more slow and steady. They're cargo horses, never known for performance. Your conversion is probably eating up some weight. Your TT is upper end for all limits. If you're going to use your old van then you have to be in the mindset of SLOW AND STEADY. You have some cooling issues. Go to the biggest radiator with the biggest fan you can fit. Go with the biggest transmission cooler you can fit. CHECK your brakes. They are light for what you're pulling. Now relax, slow down, and enjoy the journey. BTW/ For short trips to shows I sometimes tow my TT with my 1987 CROWN VICTORIA. That gets people's attention.