i had an old team planter once. someone had made a 3 pt conversion for it.
the old planter worked great with this 3pt hitch
I found a picture of this one on the internet and the hitch looks just like the one i had. Note: if you build one, you must make the support runners go back far enough so that when you pickup the planter that the runners fit under the axle of the planter, as these planters were never designed to be picked up so you must support the wheels and axle.