Diff from auto to manual

[nismosil40zx]

I was wondering how different the automatic ka diff sohc was from a manual sohc diff. Could I just swap it and put it in my car? Also is there another transmissions that I could bolt up to the sr20det other then the DOHC KA(reaplacing the throw-out bearing).This is from what I have heard.I've looked around maybe not hard enough.
Thanks for you help.