Honestly, it is always better to one up your truck and trailer combo from what you currently have planed. This way in the future, if you want to expand you do not have to expand your trucking to go with it. I would say your best bet will be a tandem axle dump with a good trailer.
One other option, is build yourself a dozer truck based off of a tandem axle truck. I worked for one company that had three. Basically, it is a flat bed with beavertail on a tandem axle truck chassis. All three were set up specifically for fast movement and self sufficiency. All had a transfer pump that was hooked into the fuel tanks of the truck. You have to run on road fuel which is the only downside. They are a great option as long as you dont need to haul anything but the dozer. Of course the downside is you cannot drop the dozer off, and go get a load of dirt or stone for the job, you need to rely on someone else for materials.