Wheel Horse did not offer this attachment, so being an enterprising engineer, I crafted my own front mount dethatcher. It snaps into the front tach-a-matic of C-series and 300/400/500 series tractors (maybe not the swept axle 520's) and it can be raised and lowered using the tractor lift lever or hydraulic lift. You have to lift it when you reach the end of the row or else it will shred your lawn. However, picking up the thatch can be done in one operation by towing a rear mounted sweeper.
Selling only the dethatcher. You will need a snowblower lift flag and a suitable blower lift tube (I was using the one from my 5xi single stage blower). I have dimensions for the lift tube and you guys with welding skills should be able to easily build one from pipe using my sketch.