The disconnect is technically an overrunning coupler that can freewheel also. I used a 1/2" Proto brand ratchet adapter from Amazon, drilled out the female square to accept a 5/8 jackshaft, cut the male square off, ground one side of the rachet pawl off to freewheel in one direction, and welded a sprocket around the outside. When disengaged the shaft can turn freely inside the sprocket, engaged it locks in one direction and ratchets the other allowing the front wheel to spin faster than the rear in a turn.... similar function to a differential in a car. When engaged the front wheel immediately starts pulling if the rears slip.
Ratchet adapter on bottom.
Installed on jackshaft with sprocket welded on.
All that said, there are better options out there. Like the $130 overrunning sprocket I posted on page 1; it is made specifically for that application. My ratchet setup is holding up so far, but I feel like it is definitely the weak link. I leave it in 3x3 all the time even on the street because you cant even tell on pavement, and the front pulling really helps offroad. I only ever disengage it to peel out.
Another cheap option is an overrunning coupler for a tractor pto.... they are onky about $45 and will definitely be strong enough as I think they are rated for up to 60hp tractors. Drawbacks are they are big and heavy, and they need some cutting/welding to adapt to a bike.
The overrunning coupler is on the top right.