Go to the search box, and type in (chuck adapter plate) its a old post of mine.
Shows lots of pics of chuck mounting on the lathe headstock, rotary table,3 and 4 jaw. It should give you some idea,s
For the most part, a 3 jaw works for most jobs. As far as mounting a 3 jaw, I allways use a plain back chuck, and just flip it over and drill the hole right through. This allows easy mounting to your table. The 4 jaw has mounting bolt in the front allready. But will you need to put the chuck on a plate first? All depends on how many slots your rotary table has. 3 jaw, will go on a 6 slot table, 4 jaw will need a plate on a 6 slot table. So the table will sometimes dictate what chuck 3 or 4 jaw. If your adding a sub plate, then you can do anything you want.