I have seen similar setups dating back to 65 to 70 years ago. Hydraulics weren't very reliable in those days. In fact many dozers used winches and cables instead of hydraulics. I think it would be a shame to get rid of the wood frame. I would consider fish plating it with a piece of flat. That way you would have the strength of iron and still retain the wood. I think you could probably run a 1/4" flat between the hoist and the beam. Drill a few more holes in the hoist to bolt it to the flat and then bolt the flat to the beam, it would strong enough for anything the hoist would lift. With the fish plate in the inside, you won't see it except when the bed is raised.