can anybody tell me what the differance between j and n-bodies?

This isn't 2.2L specific.

J-bodies and N-bodies are totally different platforms. For example, J-body: Sunfire, Cavalier... N-Body: Grand Am, Alero...

j-bodies are lighter, not as structurally stiff, have a rear beam axle

n-bodies have more cross bracing in the subframes for higher rigidity, weigh more, more leg room front and rear and a rear independant suspension

Edit: I also read somewhere that the n-body has hydroformed subframe rails, where I read that I forget, but it's supposed to make the steel more rigid and allow it to be made lighter at the same time. GM uses this method to make their truck frames as well...

My assumption is that the question is the difference between J body and n body eco's. There is already a thread for that question however. Please read the forum threads before posting a question (it may have already been asked).

In regards to your question, you'll find useful information at n-body.net and j-body.org