Your tractor is about the same size as my Ford other than you have 4x4. I have the 48" by Markham and believe me it's pretty stout. If you use it properly you should be fine. I've been using mine to dig up brush and no problem. If you go bigger you may have to worry about ballast in the rear because of the added weight. I by no mean have pushed mine to its limits because right now I'm using it without any rear weight, so the tires spin before I break anything.
Wedge