I have a Wabeco D6000E
With mine it had a straight stud but the stud for the 4 post was too short and too thin. So I had to make a custom fastener making a rod bored out with inside threads at the bottom to go on my stud and a top to put the handle on to clamp it down. Mushroom top with long stem matching proper outside diameter and threads inside.
I didn't want to tap out the stud and bore a larger hole in the expensive lathe parts and wanted to be able to go back to stock and save my tooling if I sold it.
Also on mine the AXA set didn't allow the tool to go down far enough to center the tool because the bottom of the holder would touch the top of the mounting plate. Had to mill 1/8 inch off the bottom of the holders. They are still plenty strong and let me use this and not an OXA which are weaker all around.
On the original question I would bore out the bottom of the $150 value QCTP body. Take it apart and you have a block of steel to mount in the 4 jaw for a nice farewell project for your 4 post.. Then consider whether you need to make a stud extension like I had to. Also if the stud is long enough be sure it is thick enough all the way down to hold the QCTP from rocking. It wouldn't be secure enough to just be held at the bottom with the bolt on top clamping down. If not just make a custom tube adapter on the lathe to slide over the bolt to make it fit firm all the way up.