What are excavation or land clearing companies currently charging per hour/day for a medium-sized dozer with operator? I would to have a general idea of what to expect before asking for local quotes. Based on some initial feedback, it should take a D6 about 3 days to clear and pile the area. I'm located outside of Chicago.
Get a bid on the finished job rather than an hourly rate.
Unless you know and trust the contracting company there are far too many "open ends" when paying by the hour, (IMO).
Get several quotes that are very similar in performance. That is you average rate.