Rmove the (5) bolts that hold the d20 on and the bull gear is sitting there held on with a big nut to the output shaft of the tranny.
Remove that nut and the bullgear comes right off.
Scout d300 mounts the same way, but with only 4 of the 5 bolts and has its own, specific bullgear.
Jeep d300 (more common, typically slightly cheaper) uses a more common 6-bolt "round pattern" and a female "inputs" shaft arraignment, so no bullgear. But like I said, you then would need to change the tail shaft housing and output shaft of your tranny (tear down) to adapt it.
On the plus side, switching to the 6-bolt "round" pattern does open up a much broader range or transfercases and doubler options vs the Scout "texas" pattern.