Melindak,
I was in a situation almost identical to you, Tundra 5.7, 6 speed, pulling over 8,000 lbs. The Tundra pulled the load just fine but I found the ride was very stiff when towing and the Equalizer hitch tightened up to put the weight on the front axle. Not terrible, but very "stiff" feeling. I went with Timbrens and not air bags so your ride might be a bit better than mine. I'd be sitting on the Timbrens when hitched up. I was also pulling a 35 ft trailer. The Tundra pulled it fine, but I felt I needed a heavier truck to control the load better.
I went with the Ram 2500 with the Cummins engine. You certainly don't need that engine as the 5.7 Hemi would be fine for you and actually has a couple more ponies than the Tundra. The thing I like about the Ram 2500 is it has the coil spring rear suspension so when the wife and I are towing, it rides MUCH better than the Tundra did.
My 2500 is also my daily driver so that factored into the decision.
What other said is true; while the Super Duty is a fine truck too, check the other brands.
I'm not brand loyal, this is the first Ram I've ever owned and so far, after 14,000 miles it's been flawless. The fact I could get the Ram for about $10K less than a comparable Ford was a factor too.
I love the Chevy Duramax too, but the Ram turned out to be the best deal financially for me. Good luck in your quest!
BTW, I LOVED THE OLD TUNDRA; BEST TRUCK I EVER OWNED!!
