I asked it on another thread somewhere. My starter (120) is apparently a 2.7KW jobbie. Assuming that is electrical power and not Rob's suggestion of mechanical, then 2700/12 = 225A. That is turning at full load. The initial current, as it overcomes the inertia in the engine, would be much higher. For winching, I think it would be a bad idea. When you stall a winch, it would basically be a short across the battery.
I would expect most shunts would be able to take a surge current but can't offhand see on CPC what they would be rated at. I would guess a few multiples.