Hi, the clones-in-the-style-of-Dickson-for-Myford work well on the WM180 but do indeed need machining at the base to fit that annoying boss. I managed that on my 180, but it wasn't easy going. Same as Chipenter's, it was case hardened so got easier once I got through the skin, but the inside of the bore was rough and very hard to cut. However, I only had to do that job once and I am really happy with the toolpost now.
I also have one sold by Warco as suited for the WM180, ready machined for the boss etc, and I really dislike it. Not sure if it is the same as the one they offer now. It seemed to me to move a lot when tightened up, and the vertical adjustment on the holders was poor. It hides in my Cupboard of Shame with the other mistaken purchases.