can also just put a large SA cyl between the 3pt drawbar and the toplink, and run a hose to another one up front on a mast.. as you lif thte 3pt, it compresses the cyl on the 3pt, expells the oil, and thus expands the cyl on the front, lifting the plow proportionately to volume of the cyls.. IE.. a closed hyd system.. then you could for sure do the fixed pin setup.. or use a turnbuckle setup..
that's the for sure, cheap N easy way.
soundguy