the SR20 comes out of the SE-R's in the B14 chassis (which equates to being a 200SX SE-R)

swapping from an auto GA16DE to a manual SR20DE isn't the easiest swap out there. The GA16DE engine is a very good engine, there are turbokits out there also if you want to make more power. Check out nissanperformance magazine for the boosted 200SX SE info. Just trying to give you more options. Here is plenty of information to get you started on your project:

http://darksci.net/~crim/pub/nx/in.html

http://www.nissanforums.com/showthread.php?t=45029

go here and click on "sr20de drop in"
http://www.nissanperformancemag.com/february99/