Myself I don't like converted truck tractors into dumps as they really were not designed for dumps. The suspensions are not heavy enough usually the frame isn't heavy enough. The trucks usually have wrong gearing for any kind of offroad work a 10spd really isn't that great. The only tractor you really can convert to a dump is a lowbed tractor something that is good for 140,000lb gross weight.
If your looking for a truck to haul brush etc I would try find a used rolloff truck with a couple 40 yard bins.
Dealers try to put dump boxes on tractors to try get rid of the trucks as the market is flooded with used truck tractors.
For hauling what you want to haul like brush a truck with a 40 yard bin will be better then you can have a 20 yard bin for mulch and the slightly heavier materials.
You can find a good used roll-off truck easily for 35 grand I imagine those Macks have tons of miles on them. A used converted tractor with a new box and hoist your looking at 15-20 grand for the box and hydraulics so essentially the truck is only worth 15 grand as a tractor.
Keep looking your local Mack dealer has the KY jelly out looking for people to rip off.