Oh man...
No, that engine will not fit in a B12, not unless you do EXTENSIVE fabrication, like maybe a tube chassis and a fiberglass body perhaps?
The juice is not worth the squeeze, even if they gave you motor for free, it still would cost more to shove it the car than its worth. Add to that the fact that that big clunky motor is simply too heavy for the B12's chassis and turning the car will be but a dream and even launching the car is going to be a nightmare (I'm assuming you want to "bUsT a 1/4 aGaInSt sOmE mAAd fOOlZ in tYtE CiViCz")
These Sentras are great little commuters cars that respond well to *well-thought out* modifications, but most rarely reach the level of *mAAd tYtE*, either because 1.Part simply are not as cheap or accessible or 2. Owners are poor.
My suggestion is that if you are really interested in cars and tuning, learn on this one, do little modifications here and there, learn how to <i>really</i> drive, and when you're ready to step up to another level, you can, with this car or another. When you mature a little, you'll discover this car business is not as easy as what you see in the movies or in video games. Sorry to be harsh, but someone needs to say it.