ERK! That does look a bit of a swine. I think I'd be considering if it would be easier to pull the motor out altogether, or at least get the front end up in air, and drop the front of the motor down.
Your going to have to jam the motor somehow by the looks of it, being as it's a sludge box. Either that or try and borrow a cordless impact wrench, to undo the bottom pulley. That could be a swine of a job, being as you can't get good access.
A cordless impact wrench is a marvellous thing, or even a pneumatic one and a compressor.