Well the silvia would be a nice choice but seens its not transvers monted your going to have a hard time getting it to work with your sentra. If you dont care about being legale your best bet would be a GTi-R or Sunny engine, they are the transvers monted. they came from the pulsar, sentra, and sunny. the older ones had about 210 hp and the later models had about 230hp. you will have to find a USDM SR20de tranny as there trannys are AWD. If you want more info on them, check here
www.srswap.com but i still stand by what i said frist, and that is to just traid in for a SE-R sepc V sentra and save yourself the pain and money it would cost for the swap.
some info about the SR20de(t) engine. I have not heard of porting an engine to make it biger, you can stroke it, and bore it over, but your not going to get .5 leters from that. you might be able to get .25 (.2 from a stroker kit and .05 from over bore). the engines are very good though, and can make a good amount of power, 350rwhp can be had with fuel and turbo upgrades.
i dont know much about the vq25ve (think thats the engine name) engine thats in the SE-R spec V, but i do know it takes well to bolt ons, and would be covered in warenty and would be legal if you traided in for it.