I found a useful website. It's metric but has a range of vehicles (uk models) that you can then compare your TD from a towing point of view.
http://www.whattowcar.com/I chose my car, RAV4 and then randomly chose the first caravan model Abbey. Then chose the exact model of the RAV and a random Abbey model. I then adjusted the weight and dimensions of the caravan to match my TD and improved the airflow to very good. (MTPLM is the max overall weight.)
It then reports towing ability, starting on a hill, inclines etc.
In the UK we don't have the large sized trucks, seeing a F150 or a RAM is a surprise. Toyota and Lexus swap a few models over so a Landcruiser here is a Toyota and a Lexus there and we only get a few of your homegrown models. If in doubt choose something with about the same size, horsepower and weight.
It's a free website so remember what Tim McGraw says in Can't Tell Me Nothin' "free advice is worth the price you pay."
