L28?? sorry, that's not a nissan engine, but I can tell you that pretty much any engine V8 or under will fit. I've seen them with 2jzgte motors, and RB25det motors. both inline Six's that are longer than V8's.. and I can't remember where but I saw a 240z 9roughly same size engine bay) with an LS1 corvetted engine in it with a supercharger. truly badass.
S13's weigh right around 2700lbs give or take depending on model and features.
I don't have an engine swap. but would love to do that one day.. Maybe a CA18DET or SR20DET in there.
Sorry to confuse you with the motor...I'm used to hanging out in Z forums where you say "L28" and everybody knows exactly what you mean. I guess in a 'general' Nissan forum, "L28" doesn't mean anything....Thanks for the weight info though...2700 is about the same as my 280Z (with an L28 in it.)