Another point: Weight. A lot of traction, also known as tractive effort, is a function of weight.
You can have all the torque and horsepower you need, but if you can't hook it to the ground with a combination of wheel size, tread pattern and weight, all you'll get is wheel spin.
You also need to consider the effect of the rear suspension. Tractors have no suspension other than the cushioning effect of pneumatic tires. If you have leaf springs, some of the torque that you're trying to put on the ground to do work will result in twisting the rear end in the spring mounts and "winding up" the springs.
At the least, you'll have wheel hop. At the worst, you break the springs, universal joints or driveshaft.
None of the above is a "deal killer" you just need to think about matching your load to the amount of usable tractive effort you can generate without breaking things.