Yes, the 3300 breaks down easily into 2 pieces! The top 75 lbs, the base 78 lbs. There is just no reason to get an adapter involved, unless needs to be, like yours.
Nice new complete rig, just do it right, with direct to pucks. B&W is not concerned about fitting old style hitch, to new OEMs. They make a great base to connect to the OEM pucks.
I'm not suggesting this, but seems there is an option type adapter to make the square fit the round hole of some balls.
The KZs were a great FW, and hopefully still are!
Your son needs to join the forum, if he has not already.
Jerry