The 620 was never designed to fit the 2520, so no frames were made to be direct bolt on. The 720 and 725 loader that had a similar design had frames that would be a direct bolt onto the tractor, but not sure if the pins and saddle that loader connects to mounting frame would be compatible. My guess would be it is not. If you start with the utility tractor mounting frames, they could probably be modified to fit the 2520. The frames should be extended to attach to the mounting holes on ther front of the tractor where the weight bracket would bolt on and they should also be extended lower to be able to attach a cross brace under the oil pan. The first picture shows the 720 mounting frame that would bolt to row crop tractor like you have. Second picture is 620 mounting frame that would fit utility style tractor. You can see the difference in design.