Mark, just a thought, have are you familiar with Russ's truck Sour Diesel? He used a 775 can motor, planetary gearbox and LiPO pushing 25V for a truck pull. He posted a video of him smoking that motor but maybe less volts and a lighter trigger finger would be a good setup for moving heavy iron like that?
Read about Sour Diesel here;
http://www.rctruckandconstruction.co...ht=sour+diesel