Ford Repair: Improve Towing Capacity, ford clubwagon, horse stable

Question
I recently purchased a 1995 Ford Clubwagon (E-350) with a 351 engine (5.8L V8) to accommodate our growing family.  We would also like to be able to use it to tow a travel trailer.  According to Ford, the towing capacity is only 5100 lbs which is below the weight of most of the travel trailers that are large enough for our family.  We would like to tow at least 7500 lbs (but up to 10,000 lbs would be even greater).  Is it possible to refit the body of this clubwagon with a new engine and/or transmission to increase it's towing capacity?  I have seen comments of converted E-350 vans but I have yet to find any website that talks about how to do it.  My husband has replaced a transmission before and worked extensively on other cars.  Can you first tell us if it is mechanically possible?  Then can you tell us what we need to acquire to maximize towing potential (i.e. new engine, new transmission, and/or differentials or other)?  And if you are unable to answer my questions, can you direct me to a website or individual/company that can assist us?  Thank you so very much for your time and assistance!!

Answer
A truck and trailer outfit(company) would know exactly what is needed. I would like to think that a E-350 would be able to tow 5 tons. The first thing I would do is to add an external transmission cooler. And have it installed onto the front of the radiator. This will greatly improve your cooling capacity. which is the first thing you worry about when towing. I don't believe the frame/ body is an issue. Just make sure that your hitch and receiver is a Class A. Most of the strain from towing goes into the bottom end of the engine, and the transmission of course. Just look into the yellow pages under truck and trailer. A shift kit in the transmission would help tremendously. If you still cannot find help in the yellow pages. Find your nearest horse stable. Go there and ask them whom they use for assistance with towing, etc.