I made a set of lower lift arms so that I can use the smaller sears stuff. 1/2X2 flat bar, 4 swivel eyes, 2 inch hole saw, drill and welder. Material cost was around $50. Use the hole saw to make the pockets for the eyes and weld them in,then drill the holes for the lift links and your done.
I like your idea of using the spring to put some pressure on the float option.
That's what I did for the lower arms for the GTV. Took a while to get the hole saw through there.
The 8" 3-point may become trading material, as it is in rather nice shape. I thought about using it to figure out what I need to convert the 10" sleeve plow to a 3-point. But I know someone nearby that has a 12" 3-point. If I can, I would like to keep the sleeve hitch on the 10" and just add the 3-point hitch on there. Guess I need to take the plows visiting. With all 3 side-by-side, bet I can figure it out!