I may be the only one to tell you this, but don't go over 60mph, stay out of the western mountains and you should be okay. I would never have considered a fifth wheel with a 1/2 ton until I started seeing them on the road, talked to the drivers and they were happy with their setups. I had a friend get a Chevy 2500 and a fiver, took one long trip and put them both up for sale because the truck only got 11mpg unloaded and about 6mpg towing. He hated that truck. When my wife said she wanted a fiver, I told her as long as we kept the weight to half-ton level, then shopped for strong half-ton. The towing is more comfortable than with the travel trailer that weighed 3K less. And I have a truck I love that gets 20mpg commuting.
Donning flak jacket now.
I agree with most of the other posters that a standard half ton truck is not enough for an 8,000 to 9,000 pound fifth wheel, and that you should probably get a 3/4 or 1 ton truck (or at the very least a true heavy duty half such as a GM 1500HD). However, I do not necessarily agree that you need to get a diesel. I tow an 8,000 pound fifth wheel with a 2500HD gas (6.0 liter) and it is very well matched. A diesel engine, and the related transmission upgrade costs close to $10,000 nowadays and I really don't think you need it for an 8,000 pound fiver. Furthermore, the diesel engine normally reduces the payload capacity by about 700 pounds because it weighs that much more than a gas engine. This can be a significant factor for 3/4 ton trucks that don't generally have a lot of payload capacity to spare. The bottom line is that you really need to crunch your numbers and once you do I think you will conclude that a standard half ton is not enough.
Good luck with your decision.
2006 Grand Surveyor 240BH
2004 GMC Sierra 2500HD 4X4 CC LB 6.0litre 4.10 gears
18K Reese/Hidden Hitch Signature Series Hitch
Prodigy Brake Controller
CANCEL THE ORDER! I ordered an S-10 once (not for camping) and immediately after I did did I EVER get the******thrown at me. It was going to be 3-4 weeks before the order arrived, and even though I felt like an arse for doing so, I went back, apologized, and cancelled the order.
You are probably a man of your word and cancelling an order feels like you've cheated them somehow. Nothing could be further from the truth. Happens ALL the time and you have NOT bought the truck until you actually take delivery.
These folks on here are >right< and you will NOT regret the 3/4 ton. I agree the diesel is overkill for your itty bitty camper. (lol - sorry, had to do that! )
How about placing a new order for a Hemi 2500? Should be a good, safe alternative that might also be more palatable for the dealer. One would think that they would understand and appreciate you working with them on an alternative solution. Just get the larget axle ratio that they offer, and it should be a good solution given your RV size/weight.