The one I have is solid cast steel I just needed to turn it out to the right diameter to fit over a PT blade boss. It fits an FC as well. There is a recess nearly the right size on the other side. My guess is it came from a wrecking yard I just left about 3mm in the middle and filed a couple of slots in that to fit over the prongs on the blade boss.
On that eBay one you would have to turn up some kind of adaptor
I think an FC on a PT 24 base might have height issues The engine could be too high I needed to lift my PT by 20mm. With the opposite conversion need to lower by 20mm
