Towing Issues: Truck to purchase to tow a 25 - 30 fifth wheel, dodge ram2500, fifth wheel

Question
We are looking to buy a 2500hd GMC or a dodge ram2500.  We are getting mixed answers on whether to buy a diesel or gas engine.  Also some people tell us to buy an 8' bed truck and some say with the extended cab or crew cab you can go with a short bed without any special hitch.  Hope you can help us.  We want to buy the truck first then look for a fifth wheel.

Answer
BLUE  or RED is best...  

All kidding aside, this is one question that I can not answer... A lot of things go into the purchase of a truck, and I just refuse to attempt to answer this kind of question...  


Sorry but it's not my area of expertise