How many different sizes were there? I had a pair of thick ones, and a pair of thin ones, and I believe that there were some wider than the others, maybe 3010/20 and 4010/20.
I do know that they seemed to be a PIA to keep into place, not a simple design like the regular radiator screens with the spring to pull it into position.
According to the parts catalog for these pickers, there are 2 different sets. There is one set that the height of the "box" on the inside is adjustable - this set fits the 3010-3020/4010-4020. The other set is shorter to fit the height of the 2510/2520. I was able to modify a set from a 3020 to fit on my 2520 several years ago. There is a small turnbuckle with extended arms that has hooks on the ends of the rods used above the tractor hood to hold the two screens together in place - you don't use the springs that hold the standard engine screens into place.