Aussie trying to understand your trucks

Going to be buying a FW with a GVWR of less than 10,000 pounds and hopefully under 30 foot. Need to know what can tow & more importantly stop it. 2 adults & 3 kids weighing under 500 pounds. So need a 4 door pick up. Ford, Chev or GMC & Dodge seem to be the front runners. I'm a big dodge fan here in Oz. but also love Chev, and if Ford fits the bill so be it. Would I get away with a 2500 series in these trucks? The only one of these our local dealer didn't have was the Dodge, are they roomier in the rear than Ford & Chev. Im told to get one post 2011 because of some changes from that year, probably diesel. Are all 3500 series Dually's? and are these too big? Are there short bed & long bed and does it matter what i get? What else should I look for in a truck. At this stage I can only look on-line.
Cheers Mik

Most fifth wheel folks will probably tell you that the biggest truck issue is payload. If your fifth is 10,000 gross and you are carrying 500 or so pounds in the truck the payload needs to be at least 2500-2700 pounds and a little more would be better. (20 percent of 10,000 pounds on the pin, the hitch at around 200 pounds plus the 500 pounds you mention for family) You are at the high end of most three quarter ton trucks and a one ton would be ideal in your situation. I know there will be many that will tell you that the three quarter ton will do the job and has for them for many years. All three diesels have more than enough power for 10,000 pounds and all trucks will give years of good service. If you want a huge cab, check out the mega cab by Dodge and the new ones have a much higher GVWR and payload then previously.