The motor is the easy part, it's the gear reduction that is the hard part. You could probably mate a starter motor to a hand crank winch. Unfortunatly without knowing the available torque of the motor, it would be a toss-up as to how effective it would be. Once you add up a useable motor, hand crank winch, and the parts and Time to put something together that works, you would probably be time, money and frustration ahead if you purchased a ready made winch with a known rateing that will do the job. Or if really on a budget and it is something not done all that often, you could possibly just use a hand crank winch or come along to lift/tilt the bales into the truck.