Op should be able to tow that amount of weight with a 3500 SRW, heck, might even be able to do it with one of the brand new 2013-2014 3/4 ton trucks....
We love our dually, it's my daily driver....wife is 5' 2" and be driving one, on and off since 05', she loves it...get's a kick out of all the guys in their big trucks seeing this lady driving this long bed, crew cab diesel dually just as well as most of them...it is funny at times::
If it were me, I'd opt for a little more payload and go with the 350/3500 SRW truck, but again, some of the brand new 3/4 ton trucks might also work for you.