SR20DET is the turbocharged I-4 that comes in the Sylvia.
S13 was the semi-boxy body style of the 230SX's, that body style ran up until '95.
The S14 started in '95 and went until '98, although the headlights are slightly different on '97's and '98s then on previous years.
I was looking at s14's and you'll pay anywhere from $4500 to $7000 for the body. The engine itself will cost you about $2300 to $4000 depending on condition.
If you want a real project car, I would go for this. It's a true Silvia (RHD) but it needs alot of work.
http://www.titanmotorsports.com/rederhdnisi.html