First of all.. welcome!

Can you supply the group with more info on your trailer? More important than the length, is the weight and tongue weight. Also keep in mind the weight of your stuff once you have it loaded up, including your tanks. 

It's generally better to have more pulling & breaking power than less... especially if you are planning to travel through mountainous areas. So if the 1/2 ton vehicles you're looking at seem 'just enough' for what you need to pull - probably wiser to go larger. 

 - Cherie 

Have you considered a 5th Wheel instead?  When you start getting into TTs of that size, that's when 5th Wheels have some real positives. Such as safer towing, easier manuvering.  Trying to tow and back something that long is a real bear. 

It's not as simple as 1/2 ton or 3/4 ton. You really need to look at the specs of the individual models you're looking at.  Diesel will give you a lot more torgue (you'll need it!), have a longer life, and better fuel economy for the same size in gas.

To tow this particular trailer, you'll need something with at least 10,000-11,000 lbs towing ability, and 1000lb tongue weight. Minimum. More is better.  Also look at the stopping power.  

And with something that long, you'll want as much weight in the truck as you can get to help minimize sway and jack knife potential.  Something that big has great potential to 'wag the dog' as it were.  

 - Cherie 

 ****Just noticed the date on the original post was close to a year ago****

I think a 2500 is a wise choice, it gives you more flexibility down the road even if it is more then you need right now. The largest mistake RVers make in general is thinking the RV they purchase now is what they want when most will not now until, a year or two into it. Many end up upgrading both the tow vehical, (TV) and their RV in the first 36months.

The 2500 gives you payload, which is a very important number. This is the weight your truck can handle is often forgotten about, only the weight of what the TV can tow is often considered. Many people look to the 1/2 tons and think they can tow a 13000pd RV only to find it nearly sits on the ground and handles poorly. They then end up adding after market parts to try and make it better, in some cases it works and others are just out more money. Your average 1/2 tone comes with 1500pds of payload, ( some Ford Eco boost being exceptions and I think chev has one now as well with 2000pds payload), a 8500pd TT will put 1100pds on your truck while a 8500pd 5th wheel will put 1700pds on your truck. Once you add your weight, fuel and any supplies you may have in the truck you may be at the payload of your truck or way over the payload of your truck. What does this mean, some will say nothing, some will say it up is undpsafe, having done it I will say it was not a great feeling towing having many uncomfortable experiances in wind and stopping.

 With it being gas, not sure there is much of a differences as many places report diesel being much more expensive then gas. From a MPG my gas truck got me 15.5 mpg not towing and 8.9mpg towing while my diesel gets me 19mpg not towing and 15mpg towing. Where I live diesel is usually cheaper then gas and the value of a diesel when trading down the road gives you more then your money back made it my choice. Depending on where you live, the market values and how much driving you plan on doing should be factors to consider. When I bought 6 months back I was looking at gas trucks as the up front cost of the diesel was hard to overcome but I found one with very few options and a great price which made my decision easier. I think if I had of got the gas I would still be happy as long as it was a 2500 or higher truck though.

PS

 A mistake I made when looking at payload, I went to the manufactures sites and saw numbers like 3000pds of payload. What it did not tell me was this was for a basic truck with no options. Once they added carpet, AC, power options, and anything else like the tow package and upgraded tires it takes the weight of those options away from the payload number. My 1500 ram with 2600pd payload ended up with 1300pds available.