We have a D15 Series II with a loader, the tractor would need an Aux pump to get the hydraulics running at a good speed. Ours mounts to the front of the grill and was part of an Allis attachment. How ever the axle is a little light duty, on the industrial versions they had a rib that ran down the axle to stiffen it, i would recommend this mod be done to the tractor if you were to put a loader on it.
It may seem hard finding a loader to fit with out fab and machine tools, you may be better looking for an older machine with a loader already on it.