Contact Macs, ask them if it is and what sized winch it's rated for. If you're at all uncertain, get some cardboard, start cutting and folding to come up with a design and get a cradle fabbed up to bolt directly between the chassis rails. It might not sound like much on an engineering approach, but start looking up some winch cradles online and you'll soon get an idea of how simple commercial ones are and what materials they're made of. Just go up a size in plate thickness if you want some extra confidence. I've done this before with a Rangie alloy winch bar of unknown strength and it worked a treat. (Disclaimer though - I am an engineer and did do some calculations, but using the above approach for first cut design, then doing a stress analysis on it, I had WAY over engineered it!) The only problem you'll have is with airbags / crush cans - you cannot connect the cradle to the bar (or have it sitting too close behind the bar) or it will interfere with the airbag operation (ie deploy them on a low speed hit where the crush cans should have prevented them deploying).
