I would say you should swap in the skyline engine, the SR26TTDE.... Its hella fast, and its a direct drop in, the only problem is it'll cost like 1000 bucks to get one (thats shipped!) install is probably 100 dollars if you do it yourself, and you sound like a guy who knows his stuff.
Shit dawg, thanks. OH, I forgot, can I swap the auto tranny to manual too? The dealer had a 5 speed, but I didn't want it cause I didn't like the hubcap on that one, so i got the auto that had different hubcaps. This reminds me, can I put 17" hubcaps on my 14" wheels? that would look hella tite.